Multi-stage steam extraction mode coordination control method considering disturbance conversion of multiple steam extraction nodes

Abstract

The invention discloses a multi-stage steam extraction mode coordination control method considering disturbance conversion of multiple steam extraction nodes, 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 the steam extraction nodes. Coordinated control over regulation and control parameters such as the steam supply node regulating valve opening degree, the main steam valve opening degree and the water supply flow is completed through disturbance conversion and coordination controllers of all the steam extraction points. 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; in the unit control stage, the steam extraction amount of each steam extraction point is converted into the steam extraction amount of a single steam extraction node, so that stage steam extraction decoupling is achieved, the control process is simplified, and valve adjusting control is accurately conducted on the basis of the known steam extraction amount of each steam extraction node through a coordination controller and a feedback control mechanism. And the stability of the unit bearing the industrial steam supply load is ensured.

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 multi-stage industrial steam extraction nodes. Background Art

[0002] With the continuous growth of energy demand and increasingly stringent requirements for energy conservation and emission reduction, modern power systems have put forward higher requirements for the economy and operation efficiency of power generation equipment. As the core equipment of thermal power plants, the operation mode of steam turbines directly affects the economy and energy utilization efficiency of the entire power generation process. As one of the ways to improve the energy utilization efficiency of traditional steam turbine units, cogeneration units are widely used in thermal power integrated energy systems. With the large-scale access of new energy represented by wind power and photovoltaic power to the power grid and the increasingly complex forms of energy demand on the load side, conventional cogeneration units face serious challenges in peak and frequency regulation, peak shaving and valley filling, and cascade energy supply. At present, the most direct solution is to carry out moderate unit transformation of cogeneration units. The more common methods mainly include: high back pressure transformation, cylinder cutting transformation, interconnection transformation, and multi-stage exhaust transformation. After the unit is modified, the adjustment ability of the unit can be improved to a certain extent, but there are also obvious problems. In addition to the initial investment cost of the unit modification, the unit modification process will strive to meet the unit adjustment requirements and sacrifice the unit's operating economy. In addition, when the unit is completed, the original control system will be incompatible with the modified unit. It is very important to optimize the economy of the modified unit and provide an adaptive control strategy.

[0003] After the unit completes the multi-stage steam extraction transformation, due to the coupling between the multiple steam extraction nodes, the electric power of the generator set will produce complex disturbances, and the original control strategy of the unit cannot well achieve the task of smoothing the disturbance. Summary of the invention

[0004] The present invention, based on receiving grid dispatching instructions and industrial steam supply load requirements of the park, implements a multi-stage steam extraction steam supply strategy at different steam operating nodes of the cogeneration unit to meet the industrial steam supply requirements, and provides a multi-stage steam extraction mode coordinated control method that takes into account the disturbance conversion of multiple steam extraction nodes. This method realizes the distribution of the 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 operating economy of the system; in the unit control stage, the extraction amount of each extraction point is converted into the extraction amount of a single extraction node, thereby realizing the decoupling of the stage extraction and simplifying the control process, and through the coordination controller and feedback control mechanism, the valve control is accurately performed on the basis of the known extraction amount of each extraction node, ensuring the stability of the unit when it bears the industrial steam supply load.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes comprises the following steps:

[0007] Step 1: The load control system of the thermal power unit receives the dispatching instruction E from the power grid. total and the factory park industrial steam supply load instruction Q total ;

[0008] Step 2: Scheduling instruction E total and industrial steam supply load instruction Q total As the input signal, the steam supply of each extraction node of each unit is completed through the thermal load distribution algorithm of the cogeneration unit to obtain the distributed electrical load E of each unit. i The steam extraction volume S corresponding to each steam extraction point i ’ ;

[0009] 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;

[0010] Step 4: convert the steam extraction amount of each level of industrial steam extraction nodes into the steam extraction amount of the main steam extraction point in the industrial steam extraction, and uniformly regard it as the steam extraction disturbance of the steam extraction point, and use the PID controller of the steam extraction to control it;

[0011] Step 5: Set the main steam pressure P z0 The rated parameter and the steam supply converted to the main steam extraction point are used as signals to input into the coordination controller, and a set of control loops are added 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 industrial steam supply valves at all levels i ;

[0012] Step 6: The main valve opening u obtained by the coordinated controller output T 、Fuel quantity u B , water flow rate D fw Unit parameters and various levels of industrial steam supply valve opening signals a i Acts on combined heat and power units;

[0013] Step 7: The main steam pressure P obtained from the actual operation of the unit z And the actual industrial steam extraction volume S of each level of steam extraction node i As feedback signals, they act on their respective controllers to form a closed loop, completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 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;

[0016] 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;

[0017] 3) Coordinated control research can realize automatic control of the regulating valve of the cogeneration unit and reduce manpower input;

[0018] 4) By uniformly converting the industrial steam supply of multiple extraction nodes into the industrial steam supply of the main extraction point, the decoupling of multiple extraction points can be achieved. After using disturbance conversion, compared with the independent control of each extraction node, multiple controllers can be reduced to one controller, which is convenient for controller setting. At the same time, after conversion, the mutual influence between the industrial extraction points can be reduced, making the power generation process more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the schematic diagram of the disturbance 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 provides a multi-stage steam extraction mode coordinated control method considering the disturbance conversion of multiple steam extraction nodes for the cogeneration unit that undertakes high-load industrial steam supply and contains multiple industrial steam supply nodes, with the goal of economic operation and stable control of the system, and combines the thermal power load distribution algorithm based on the genetic algorithm to complete the industrial steam supply S between each steam extraction node. i ’ The coordinated control of the steam supply node regulating valve opening, main steam valve opening, feed water flow and other control parameters is completed through the disturbance conversion and coordination controller of each extraction point. The coordinated control principle of multiple extraction modes of the unit under single unit condition is as follows: Figure 1 As shown, the method specifically comprises the following steps:

[0023] Step 1: The load control system of the thermal power unit receives the dispatching instruction E from the power grid. total and the factory park industrial steam supply load instruction Q total .

[0024] In this step, for the multi-extraction steam cogeneration units, the industrial steam supply load instruction is the primary requirement to be met. The cogeneration units participating in high-load industrial steam supply are less likely to undertake grid peak load regulation and frequency regulation tasks than other cogeneration units without affecting the grid dispatching instructions.

[0025] Step 2: Scheduling instruction E total and industrial steam supply load instruction Q total As the input signal, the steam supply of each extraction node of each unit is completed through the thermal load distribution algorithm of the cogeneration unit to obtain the distributed electrical load E of each unit. i , the steam extraction volume S corresponding to each steam extraction point i ’ .

[0026] In this step, the minimum economic heat consumption of the overall operation of the thermal power unit load control system is taken as the optimization target, and the dispatching instruction E total and industrial steam supply load instruction Q total is the input, and each unit is assigned an electrical load E i , the steam extraction volume S corresponding to 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 steam supply of each extraction node of each unit. The specific steps are as follows: determine whether the unit is in operating condition, and include the unit in operating condition into the optimization range; the algorithm program receives the dispatching instruction E received by the load control system of the thermal power unit total and industrial steam supply load instruction Q total ; Set the threshold of each node according to the actual operation of the unit (power limit of units #1 and #2, steam extraction limit of each industrial steam extraction node of units #1 and #2); construct the optimization objective function; solve the minimum value of the objective function iteratively through particle swarm optimization; obtain the steam supply of each steam extraction node of each unit.

[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, the regulating valve of the third extraction point of the intermediate pressure cylinder is put into operation, and the opening of the regulating valve is controlled to be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% in sequence, and the steam flow rate under each regulating valve opening is recorded; the regulating valve of the cold re-extraction is put into operation, and the opening of the regulating valve is controlled to be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% in sequence. 60%, 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: Convert the steam extraction capacity of each level of industrial steam extraction nodes into the steam extraction capacity of the main steam extraction points that are widely used in industrial steam extraction (for example, the steam extraction capacity of the third steam extraction point of the medium pressure cylinder), and uniformly regard them as the steam extraction disturbance of the steam extraction point, and use the PID controller of the steam extraction for control.

[0031] In this step, the control of the steam extraction amount at the target steam extraction point is completed based on the disturbance conversion test of multiple steam extraction nodes. The specific steps of the disturbance conversion test are as follows: Step 1, select the target steam extraction point A for conversion, and independently start steam extraction at point A and increase the steam extraction amount from 0t / h to the maximum steam extraction amount of point A in sequence, and record the effect of the steam extraction amount at point A on the system main steam pressure P in the process. z The disturbance of the unit parameters; Step 2, sequentially put the remaining extraction points into operation, and gradually increase the extraction capacity of the extraction points from 0t / h to their maximum extraction capacity, with the main steam pressure P of the system in step 1 z The disturbance is taken as the benchmark, and the extraction amount of the remaining extraction points when the same disturbance as that of point A in step 1 is recorded; step 3, based on steps 1 and 2, the disturbance relationship curves of the remaining extraction points relative to the extraction point A can be obtained, and the disturbance conversion test is completed accordingly to guide the calculation; step 4, complete the PID control.

[0032] Taking the three-stage extraction steam cogeneration unit with the third extraction point of the intermediate pressure cylinder, the cold re-extraction point and the hot re-extraction point as an example, the specific disturbance conversion test mainly includes the following steps: Step 1, the third extraction point is used for extraction and the extraction volume is increased from 0t / h to the maximum extraction volume of the third extraction point in sequence, and the effect of the extraction volume of the third extraction point of the intermediate pressure cylinder on the main steam pressure P of the system is recorded in the process. z Disturbance of unit parameters; Step 2, put cold re-extraction steam into operation separately, and gradually increase the cold re-extraction steam capacity from 0t / h to the maximum working condition of cold re-extraction steam, taking the system main steam pressure P in step 1 as z The disturbance of the unit parameters is taken as the benchmark, and the corresponding cold re-extraction volume when the same disturbance is reached in step 1 is recorded, and this is used as the disturbance benchmark; step 3, the hot re-extraction point is independently put into steam extraction and the steam extraction volume is increased from 0t / h to the maximum steam extraction volume of the hot re-extraction point in sequence, and the main steam pressure P of the system in step 1 is set to z The disturbance of the unit parameters is used as a benchmark, and the hot re-extraction amount corresponding to the same disturbance in step 1 is recorded; step 4, based on steps 1 to 3, a disturbance-cold re-extraction amount-third extraction amount-hot re-extraction amount characteristic curve can be drawn, and on this basis, the cold re-extraction amount and the hot re-extraction amount are converted into the extraction amount of the third extraction point of the intermediate pressure cylinder that is easy to control.

[0033] Step 5: Set the main steam pressure P z0 The rated parameter and the steam supply converted to the main steam extraction point are used as signals to input into the coordination system, and a set of control loops are added 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 industrial steam supply valves at all levels i .

[0034] In this step, the main steam pressure is used as the rated parameter of the unit, which is set according to the unit's own conditions and load requirements. The main purpose is to ensure stable operation of the unit.

[0035] Step 6: The main valve opening u obtained by coordinating the system output T 、Fuel quantity u B , water flow rate D fw Unit parameters and various levels of industrial steam supply valve opening signals a i Applicable to combined heat and power units.

[0036] In this step, the main valve opening u is obtained based on the debugged multi-input multi-output coordinated controller. T 、Fuel quantity u B , water flow rate D fw Unit parameters and various industrial steam supply valve opening signals a iThe key to coordinated control is the exchange and feedback of real-time information, ensuring that each subsystem can be adjusted according to the overall goal. The valve opening signal of each level of industrial steam supply is i The determination is based on the steam extraction volume at each extraction point in step three and the flow characteristic curve of the regulating valve selected for each extraction point.

[0037] Step 7: The main steam pressure P obtained from the actual operation of the unit z And the actual industrial steam extraction volume S of each level of steam extraction node i As feedback signals, they act on their respective controllers to form a closed loop, completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

Claims

1. A coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes, characterized in that The method comprises the following steps: Step 1: The load control system of the thermal power unit receives the dispatching instruction E from the power grid. total and the factory park industrial steam supply load instruction Q total ; Step 2: Use the scheduling instruction E total and industrial steam supply load instruction Q total As the input signal, the steam supply of each extraction node of each unit is completed through the thermal load distribution algorithm of the cogeneration unit to obtain the distributed electrical load E of each unit. i The steam extraction volume S corresponding to each steam extraction point i ’ ; 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: convert the steam extraction amount of each level of industrial steam extraction nodes into the steam extraction amount of the main steam extraction point in the industrial steam extraction, and uniformly regard it as the steam extraction disturbance of the steam extraction point, and use the PID controller of the steam extraction to control it; Step 5: Set the main steam pressure P z0 The rated parameter and the steam supply converted to the main steam extraction point are used as signals to input into the coordination controller, and a set of control loops are added 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 industrial steam supply valves at all levels i ; Step 6: The main valve opening u obtained by the coordinated controller output T 、Fuel quantity u B , water flow rate D fw Unit parameters and various levels of industrial steam supply valve opening signals a i Acts on combined heat and power units; Step 7: The main steam pressure P obtained from the actual operation of the unit z And the actual industrial steam extraction volume S of each level of steam extraction node i As feedback signals, they act on their respective controllers to form a closed loop, completing the coordinated control of the cogeneration unit under the multi-extraction steam mode.

2. The coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes according to claim 1 is characterized in that In the step 2, the minimum economic heat consumption of the overall operation of the thermal power unit load control system is taken as the optimization target, and the dispatching instruction E received by the thermal power unit load control system total and industrial steam supply load instruction Q total is the input, and each unit is assigned an electrical load E i , the steam extraction volume S corresponding to each steam extraction node i ’ As the output, the steam supply of each extraction node of each unit is completed based on the thermal and electric load distribution algorithm of the cogeneration unit.

3. The coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes according to claim 2 is characterized in that The specific steps of completing the steam supply of each extraction node of each unit based on the heat and power cogeneration unit heat and power load distribution algorithm are as follows: judging whether the unit is in operating condition, and the units in operating condition are included in the optimization range; the algorithm program receives the dispatching instruction E received by the load control system of the thermal power unit; total and industrial steam supply load instruction Q total ; Set the threshold of each node according to the actual operation of the unit; construct the optimization objective function; solve the minimum value of the objective function iteratively through particle swarm optimization; obtain the steam supply of each extraction node of each unit.

4. The coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes 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.

5. The coordinated control method for multi-stage steam extraction modes considering disturbance conversion of multiple steam extraction nodes according to claim 4 is 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.

6. The coordinated control method of multi-stage steam extraction mode considering disturbance conversion of multiple steam extraction nodes according to claim 1 is characterized in that In step 4, the control of the steam extraction amount at the target steam extraction point is completed based on the disturbance conversion test of multiple steam extraction nodes. The specific disturbance conversion test steps are: Step 1: Select the target extraction point A, start extraction at point A and increase the extraction capacity from 0 t / h to the maximum extraction capacity at extraction point A. Record the effect of extraction capacity at point A on the main steam pressure P of the system. z Disturbance of unit parameters; Step 2: Sequentially put the remaining steam extraction points into operation and gradually increase the steam extraction capacity of the steam extraction points from 0 t / h to their maximum steam extraction capacity. z Taking the disturbance of as the benchmark, record the steam extraction amount of other steam extraction points when the same disturbance as that of point A in step 1 is achieved; Step 3: Based on Step 1 and Step 2, the disturbance relationship curves of the remaining steam extraction points relative to the A steam extraction point are obtained, and the disturbance conversion test is completed accordingly to guide the calculation; Step 4: Complete PID control.

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