Multi-steam extraction mode coordination control method for economical operation of steam turbine

Abstract

The invention discloses a multi-steam-extraction-mode coordination control method for economical operation of a steam turbine, and the method is combined with a thermoelectric load distribution algorithm based on a genetic algorithm to complete the distribution of the industrial steam supply amount among steam extraction nodes. Coordinated control over regulation and control parameters such as the opening degree of a steam supply node regulating valve, the opening degree of a main steam valve and the water supply flow is completed through the debugged coordination controller. According to the method, through a thermoelectric load distribution algorithm based on a genetic algorithm, the distribution work of the steam extraction amount of each node of the multi-steam extraction node combined heat and power generation unit is realized, the overall heat consumption of the system is further reduced, and the operation economy of the system is improved; through the coordination controller and the feedback control network, valve adjusting control is accurately carried out on the basis that the steam extraction amount of each steam extraction node is known, and the stability of the unit is guaranteed when the unit bears the industrial steam supply load.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation system control, and relates to a control method for a cogeneration unit, and specifically to an economic control method for a cogeneration unit with a multi-stage industrial steam extraction node. Background Art

[0002] With the continuous increase in global energy demand and increasingly stringent energy conservation and emission reduction policies, modern power systems have put forward more stringent requirements on the economy, flexibility and operating efficiency of power generation equipment. As the core power equipment of thermal power plants, the operation mode of steam turbines directly affects the efficiency and cost of the entire power production process. Therefore, optimizing the operation mode of steam turbines is crucial to improving the overall energy utilization rate. As a traditional technology that can improve the comprehensive utilization efficiency of energy, cogeneration units are widely used in thermal power integrated energy systems. They maximize the use of fuel energy by providing dual outputs of electricity and heat. However, with the large-scale access of renewable energy represented by wind power and photovoltaics to the power grid, as well as the trend of diversification and increasing volatility of energy demand at the user end, traditional cogeneration units are facing increasingly severe challenges in terms of regulation capacity, load tracking and efficient operation.

[0003] One of the measures currently commonly taken to improve the regulation capability and flexibility of cogeneration units is to transform existing units. These transformation methods include but are not limited to high back pressure transformation, cylinder cutting transformation, interconnection transformation and multi-stage air extraction transformation. Through these technical transformations, the regulation performance of the unit can be effectively improved, enabling it to better cope with frequent fluctuations in the power grid and load changes. However, although these transformations have optimized the regulation capability of the unit to a certain extent, they are also accompanied by a series of problems. First, unit transformation often requires a high initial investment, which poses a challenge to the financial pressure of power companies. Secondly, in order to meet the new regulation requirements, the transformation often sacrifices the operating economy of the unit, resulting in reduced efficiency of the unit during load regulation and even increased operating costs. In addition, there may be a mismatch between the transformed unit and the original control system, and the original control strategy and optimization algorithm may not be able to adapt to the new operating state, thus affecting the overall performance of the unit.

[0004] Industrial steam-supply cogeneration units with multiple extraction nodes have added many extraction nodes on the basis of conventional cogeneration units, and the steam supply method adopts the method of evenly distributing the heat supply to each unit without considering the unit conditions. Firstly, there is a large room for optimization of the operating economy of the unit, and secondly, the newly added extraction valves at each level lack suitable regulating controllers. Summary of the invention

[0005] The present invention provides a method for coordinated control of multiple steam extraction modes for economic operation of steam turbines for cogeneration units that have completed multi-stage steam extraction transformation and have high requirements for industrial steam supply loads in industrial parks and grid dispatching loads. The method realizes the distribution of steam extraction amount of each node of the cogeneration unit with multiple steam extraction nodes through a thermal power load distribution algorithm based on a genetic algorithm, further reducing the overall heat consumption of the system and improving the economic operation of the system; the valve control is accurately performed based on the known steam extraction amount of each steam extraction node through a coordinated controller and a feedback control network, ensuring the stability of the unit when it bears the industrial steam supply load.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine. First, a thermal power load distribution algorithm with the heat consumption of the park cogeneration system as the target is used to obtain the electrical load borne by each unit in the cogeneration system and the steam extraction capacity of each steam extraction node; then, based on the obtained steam extraction capacity of each steam extraction node, the steam extraction point regulating valve opening is obtained in combination with the regulating valve flow characteristic curve and an independent PID controller, and the opening of each steam extraction regulating valve is input into the coordinated controller of the cogeneration unit together with the rated operating parameters of the unit; finally, the actual steam extraction capacity of the unit and the main steam pressure are used as feedback signals to form a closed loop before the coordinated control to complete the coordinated control. Specifically, the following steps are included:

[0008] Step 1: Read the electric load E and industrial steam supply load Q borne by the combined heat and power system;

[0009] Step 2: complete the thermal power load distribution of each unit at each steam extraction point through a load distribution algorithm that takes the overall heat consumption of the cogeneration system as the optimization target;

[0010] Step 3: Obtain the flow characteristic curves of the regulating valves at each level of industrial steam extraction nodes through experiments, so as to control the industrial steam extraction volume;

[0011] Step 4: Establish independent PID controllers one by one for each steam extraction node of the unit to control it;

[0012] Step 5: Set the main steam pressure P 0 , as the rated parameters and the steam supply of each industrial steam supply and extraction node as a signal input into the coordinated control system, add a set of control loops, and obtain the main valve opening u of the cogeneration unit T 、Fuel quantity u B , water flow rate D fw And the opening of industrial steam supply valves at all levels i ;

[0013] Step 6: Obtain the main valve opening u from the coordinated control system T 、Fuel quantity uB , water flow rate D fw And the opening of industrial steam supply valves at all levels i The signal acts on the combined heat and power unit;

[0014] Step 7: The main steam pressure P obtained from the actual operation of the unit z , Industrial steam extraction volume S of each level of steam extraction node i The feedback signals act on the input values ​​of each variable before coordinated control to form a closed loop, thus completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1) The distribution of steam extraction between various steam extraction nodes through advanced thermal power load distribution methods can further improve the operating economy of the system;

[0017] 2) Coordinated control can alleviate the impact of high-load industrial steam supply on unit parameters such as the main steam pressure of the unit, ensuring the safe and stable operation of the system;

[0018] 3) Coordinated control research can realize automatic control of the regulating valve of the cogeneration unit and reduce manpower input. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the schematic diagram of coordinated control of multiple steam extraction modes for a single unit;

[0020] Figure 2 The flow chart of the thermal power load allocation method is shown in FIG. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0022] As the most critical energy hub in the heat-electricity integrated energy system, the improvement of the operation economy of the cogeneration unit can greatly improve the economic level of the entire system. The present invention is aimed at the cogeneration unit that undertakes high-load industrial steam supply and contains multiple industrial steam supply nodes. With the economic operation and stable control of the system as the goal, it provides a multi-extraction mode coordinated control method for the economic operation of the steam turbine. The industrial steam supply distribution between the steam extraction nodes is completed by combining the thermal power load distribution algorithm based on the genetic algorithm, and the coordinated control of the regulating parameters such as the valve opening, the main steam valve opening, and the feed water flow of the steam supply node is completed through the debugged coordinated controller. The principle of coordinated control of multiple extraction modes of a single unit is as follows Figure 1 As shown, the method specifically comprises the following steps:

[0023] Step 1: Read the electric load E and industrial steam load Q borne by the combined heat and power system.

[0024] In this step, based on the industrial steam supply requirements of the industrial park and the dispatching instructions of the power grid dispatching center for the cogeneration system, the electric load E and the industrial steam supply load Q borne by the cogeneration system are read.

[0025] Step 2: The thermal load distribution of each unit at each steam extraction point is completed by using a thermal load distribution algorithm for the cogeneration unit with the overall heat consumption of the cogeneration system as the optimization target.

[0026] In this step, the electric load E and industrial steam supply load Q are used as inputs, and the load of each unit e i , Steam extraction volume S of each steam extraction node i For output, based on Figure 2 The heat and power load distribution algorithm of the cogeneration unit shown in the figure completes the heat and power load distribution of each unit at each steam extraction point. The main load distribution process of the heat and power load distribution algorithm is: determine whether the unit is in operating condition, and include the units in operating condition into the optimization range; the algorithm program accepts load instructions (electric load E and industrial steam supply load Q); sets the threshold of each node according to the actual operation of the unit (power limit of #1 and #2 units, steam extraction limit of each industrial steam extraction node of #1 and #2 units); constructs the algorithm optimization objective function; solves the minimum value of the objective function iteratively through particle swarm optimization; and obtains the heat and power load distribution target of each unit at each steam extraction node.

[0027] Step 3: Obtain the flow characteristic curves of the regulating valves at each level of industrial steam extraction nodes through experiments to control the industrial steam extraction volume.

[0028] In this step, the industrial steam extraction volume control is completed based on the flow characteristic measurement test of each regulating valve. The specific steps are as follows: the steam extraction regulating valves are put into operation in sequence, and the steam extraction regulating valves are installed at each industrial steam extraction node. The actual flow of the regulating valve outlet under different regulating valve openings is recorded, and the flow characteristic curves of each level of regulating valves are fitted through a difference function or a regression equation to control the industrial steam extraction volume. The method for obtaining the flow characteristic curves of each level of regulating valves is: the regulating valve opening is controlled to be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% in sequence, and the steam flow under each regulating valve opening is recorded, and the flow characteristic curve of the regulating valve is further fitted.

[0029] Taking the three-stage steam extraction cogeneration unit with the third extraction point of the intermediate pressure cylinder, cold re-extraction and hot re-extraction as an example, first put the third extraction point regulating valve into operation, and control the regulating valve opening to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% in sequence, and record the steam flow at each regulating valve opening; put the cold re-extraction regulating valve into operation, and control the regulating valve opening to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% in sequence. 0%, 70%, 80%, 90%, 100%, and record the steam flow rate at each regulating valve opening; put the hot re-extraction regulating valve into operation, control the regulating valve opening to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% in sequence, and record the steam flow rate at each regulating valve opening; after data collection is completed, curve fitting is performed through the difference function or regression equation to obtain the flow characteristic curve of the regulating valve of each industrial extraction node.

[0030] Step 4: Establish independent PID controllers for each steam extraction node of the unit one by one for control.

[0031] In this step, the flow characteristic curve of the regulating valve under the extraction condition of each extraction node and the disturbance relationship of the extraction disturbance of each extraction node to the main steam pressure of the unit are determined through the disturbance test on the unit site, and an independent PID controller is established to control each extraction node of the unit. The specific control method is: different industrial extraction nodes are controlled one by one, first the main steam supply node regulating valve control is carried out, and the other steam supply nodes are not put into use. The PID controller is set by the influence of the main steam supply node regulating valve opening 0-100% on the main steam pressure; keep the main steam supply regulating valve opening unchanged, open the other steam supply regulating valves 0-100% one by one according to the proportion of steam supply, and set the PID controller according to the disturbance situation.

[0032] Taking the three-stage steam extraction of the third extraction point, cold re-extraction and hot re-extraction as an example, the characteristic functions of the three extraction valves are established respectively: 1. Under the condition that cold re-extraction and hot re-extraction are not put into operation, the opening of the third extraction regulating valve varies in the range of 0-100%, and the corresponding values ​​of the unit parameters such as the main steam pressure during the disturbance are recorded; 2. The third extraction point maintains an opening of 80%, the hot re-extraction is not put into operation, the cold re-extraction regulating valve varies in the range of 0-100%, and the corresponding values ​​of the unit parameters such as the main steam pressure during the disturbance are recorded; 3. The third extraction point maintains an opening of 100%, the cold re-extraction maintains an opening of 80%, the hot re-extraction regulating valve opening varies in the range of 0-100%, and the corresponding values ​​of the unit parameters such as the main steam pressure during the disturbance are recorded.

[0033] Step 5: Set the main steam pressure P 0As the rated parameter and the steam supply of each level of industrial steam supply and extraction node as a signal input into the coordinated control system, add a set of control loops to obtain the main valve opening u of the cogeneration unit T 、Fuel quantity u B , water flow rate D fw And the opening of each industrial steam supply valve a i .

[0034] Step 6: The main valve opening u obtained in step 5 is T 、Fuel quantity u B , water flow rate D fw And the opening of each industrial steam supply valve a i The signal acts on the combined heat and power unit.

[0035] In this step, the main valve opening u is obtained based on the debugged multi-input multi-output coordinated control system. T 、Fuel quantity u B , water flow rate D fw And the opening of each industrial steam supply valve a i The key to signal and coordinated control is the exchange and feedback of real-time information to ensure that each subsystem can be adjusted according to the global goal.

[0036] Step 7: The main steam pressure P obtained from the actual operation of the unit z , Industrial steam extraction volume S of each level of steam extraction node i The feedback signals act on the input values ​​of each variable before coordinated control to form a closed loop, thus completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

Claims

1. A method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine, characterized in that The method comprises the following steps: Step 1: Read the electric load E and industrial steam supply load Q borne by the combined heat and power system; Step 2: complete the thermal power load distribution of each unit at each steam extraction point through a load distribution algorithm that takes the overall heat consumption of the cogeneration system as the optimization target; Step 3: Obtain the flow characteristic curves of the regulating valves at each level of industrial steam extraction nodes through experiments, so as to control the industrial steam extraction volume; Step 4: Establish independent PID controllers one by one for each steam extraction node of the unit to control it; Step 5: Input the set main steam pressure P0 as the rated parameter and the steam supply of each industrial steam supply and extraction node as a signal into the coordinated control system, add a set of control loops, and obtain the main valve opening u of the cogeneration unit. T 、Fuel quantity u B , water flow rate D fw And the opening of industrial steam supply valves at all levels i ; Step 6: Obtain the main valve opening u from the coordinated control system T 、Fuel quantity u B , water flow rate D fw And the opening of industrial steam supply valves at all levels i The signal acts on the combined heat and power unit; Step 7: The main steam pressure P obtained from the actual operation of the unit z , Industrial steam extraction volume S of each level of steam extraction node i The feedback signals act on the input values ​​of each variable before coordinated control to form a closed loop, thus completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

2. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 1, characterized in that In the step 1, based on the industrial steam supply requirements of the industrial park and the dispatching instructions of the power grid dispatching center for the cogeneration system, the electric load E and the industrial steam supply load Q borne by the cogeneration system are read.

3. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 1, characterized in that In step 2, the electric load E and the industrial steam supply load Q are used as inputs, and the load of each unit e i , Steam extraction volume S of each steam extraction node i As the output, the thermal load distribution of each unit at each extraction point is completed based on the thermal load distribution algorithm of the cogeneration unit.

4. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 3, characterized in that The process of completing the thermal power load distribution of each unit at each steam extraction point based on the thermal power load distribution algorithm of the cogeneration unit is as follows: judging whether the unit is in an operating condition, and including the unit in an operating condition in the optimization range; the algorithm program accepts load instructions; sets the threshold of each node according to the actual operating conditions of the unit; constructs an algorithm optimization objective function; iteratively solves the minimum value of the objective function through particle swarm optimization; and obtains the thermal power load distribution target of each unit at each steam extraction node.

5. The multi-extraction mode coordinated control method for economic operation of a steam turbine according to claim 1 is characterized in that In the step three, the industrial steam extraction volume control is completed based on the flow characteristic measurement test of each regulating valve. The specific steps are as follows: the steam extraction regulating valves are put into operation in sequence, and the steam extraction regulating valves are installed at each industrial steam extraction node. The actual flow of the regulating valve outlet under different regulating valve openings is recorded, and the flow characteristic curves of each level of regulating valves are fitted through a difference function or a regression equation to control the industrial steam extraction volume.

6. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 5, characterized in that The method for obtaining the flow characteristic curve of each level of the regulating valve is: controlling the opening of the regulating valve to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% in sequence, recording the steam flow at each regulating valve opening, and further fitting to obtain the flow characteristic curve of the regulating valve.

7. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 1, characterized in that In step 4, the flow characteristic curve of the regulating valve under the extraction condition of each extraction node and the disturbance relationship of the extraction disturbance of each extraction node to the main steam pressure of the unit are determined through the disturbance test on the unit site, and an independent PID controller is established to control each extraction node of the unit.

8. The method for coordinated control of multiple steam extraction modes for economic operation of a steam turbine according to claim 7, characterized in that The specific control method of each steam extraction node is as follows: different industrial steam extraction nodes are controlled successively, and the main steam supply node valve control is performed first, and the remaining steam supply nodes are not put into use. The PID controller is set according to the influence of the main steam supply node valve opening of 0 to 100% on the main steam pressure; the main steam supply valve opening is kept unchanged, and the remaining steam supply valves are opened by 0 to 100% in turn according to the proportion of steam supply, and the PID controller is set according to the disturbance situation.

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