A Modeling Method for Steam Turbine Speed Control and Protection System Based on Timed Automata

Abstract

The present invention discloses a modeling method for a steam turbine speed control and protection system based on timed automata, belonging to the technical field of steam turbine speed control and protection systems. Based on the traditional steam turbine speed control and protection functions, the present invention simplifies them without changing the original control and protection logic; focuses the implementation of the control and protection logic functions on specific physical devices such as the main steam valve, control valve, steam turbine, speed sensor, and trip valve, and formally models these devices using the theory of timed automata. The traditional model cannot describe the transitions of various operating conditions of the steam turbine and the operating processes of various types of devices under each operating condition, while the timed automata model of the present invention can better display the process of sequential control and protection of the steam turbine system, and has the advantages of simple model, accurate logic, excellent dynamic performance, high reliability, etc., greatly reducing the repeatability and complexity of the modeling process.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine speed control and protection systems, and particularly relates to a modeling method for a steam turbine speed control and protection system based on timed automata. Background Art

[0002] The formal method is a special type of mathematical analysis method that can refine and construct corresponding mathematical symbols for a modeling object or related theory, thereby obtaining a set of concise and appropriate descriptive models. Timed automata is a type of formal method, which has the important characteristics of exchanging information with the outside world in real time and changing its own working state according to the exchanged information. However, so far, the research and application of timed automata theory in the field of steam turbine speed control and protection are almost zero. For the speed control and protection function of a steam turbine, the control and protection logic is the core of the entire system. However, for traditional models represented by differential equations or difference equations, the description of the control logic is complex and very cumbersome, and most of them cannot well reflect the dynamic process of the system. Summary of the Invention

[0003] Aiming at the problem that traditional models cannot describe the transitions of various operating conditions of a steam turbine and the operation processes of various types of equipment under each operating condition, the purpose of the present invention is to provide a modeling method for a steam turbine speed control and protection based on timed automata, which can more effectively depict the core control and protection logic of the system and more completely reflect the dynamic process of the system.

[0004] The technical solution for achieving the purpose of the present invention is as follows:

[0005] A modeling method for a steam turbine speed control and protection system based on timed automata, comprising:

[0006] Establishing a steam turbine speed control and protection system model: T A =(S A , S A0 , Σ A , E A )

[0007] Wherein, S A0 is the initial state set S A0 ;

[0008] S A0 =(c m , c a , c q , slow, c u )

[0009] Wherein, c m , c a , c q , slow, c uThey respectively represent the main steam valve closed state, the control valve closed state, the turbine closed state, the normal speed state of the speed sensor, and the emergency stop valve closed state.

[0010] S A is the state set;

[0011] S A ={S A0 , S A1 , S A2 , S A3 , S A4 , S A5 , S A6 , S A7}}

[0012] Among them, S A1 , S A2 , S A3 , S A4 , S A5 , S A6 , S A7 respectively represent the semi-start state, semi-opening start state, full-opening start state, overspeed alarm state, emergency stop state, deceleration state, and semi-closed state of the system.

[0013] S A1 =(s m , c a , s t , slow, c u );

[0014] S A2 =(s m , s h , s q , slow, c u );

[0015] S A3 =(s m , s a , s q , slow, c u );

[0016] S A4 =(s m , c a , s t , fast, c u );

[0017] S A5 =(s m , s a , s q , fast, s u );

[0018] S A6 =(c m ,c a ,c q ,fast,s u );

[0019] S A7 ={c m ,c a ,c q ,slow,s u ).

[0020] Among them, s m represents the opening state of the main steam valve; s t represents the semi-opening state of the steam turbine; s q represents the starting state of the steam turbine; s h represents the semi-opening state of the regulating valve; s a represents the fully open state of the regulating valve; s u represents the opening state of the emergency stop valve; c u represents the closed state of the emergency stop valve; fast represents the overspeed alarm state of the speed sensor.

[0021] ∑ A is the event trigger set;

[0022] ∑ A =(k m ,k a ,k h ,k u ,u,g u ,g a ,g m ,v>v max ,v<v max )

[0023] Among them, k m represents the opening command of the main steam valve; k a represents the semi-opening command of the regulating valve; k h represents the fully open command of the regulating valve; k u represents the opening command of the emergency stop valve; u represents the emergency stop command of the main steam valve issued by the emergency stop valve; g u represents the closing command of the emergency stop valve; g a represents the closing command of the regulating valve; g m represents the closing command of the main steam valve; v max represents the speed threshold of the steam turbine; v>v max represents the overspeed of the steam turbine; v<v max represents the normal speed of the steam turbine.

[0024] E A is the state transition set;

[0025] E A = {δ1, δ2, δ3, δ4, δ5, δ6, δ7, δ8, δ9, δ 10 , δ 11}

[0026] Among them, represents that after the main steam valve is opened, the system transfers from the initial state to the semi-start state; represents that after the regulating valve is opened to half opening, the system transfers from the semi-start state to the half-opening start state; represents that after the regulating valve is opened to full opening, the system transfers from the semi-start state to the full-opening start state; represents that after the regulating valve is closed, the system transfers from the half-opening start state to the semi-start state; represents that after the regulating valve is closed, the system transfers from the full-opening start state to the semi-start state; represents that after the main steam valve is closed, the system transfers from the semi-start state to the initial state; represents that when the steam turbine is overspeed, the system transfers from the start state to the overspeed alarm state; represents that after the emergency stop valve is opened, the system transfers from the overspeed alarm state to the emergency stop state; represents that after the main steam valve is emergently shut off, the system transfers from the emergency stop state to the deceleration state; represents that after the rotational speed of the steam turbine is lower than the detection threshold, the system transfers from deceleration to the semi-closed state; and represents that after the emergency stop valve is closed, the system transfers from the semi-closed state to the initial state.

[0027] Compared with the prior art, the remarkable advantages of the present invention are:

[0028] The formal model provided by the present invention, because its basic semantics is closely related to clocks and system logic, can well depict the control and protection logic of the system for a real-time rotational speed control and protection system such as a steam turbine. Secondly, because the automaton has the important feature of exchanging information with the outside world in real time and changing its own working state according to the obtained information, it can also more completely reflect the dynamic process of the system. Compared with the existing models, the present invention can effectively depict the control and protection logic process of the steam turbine rotational speed control and protection system, and at the same time, due to its own instantaneity, it can more completely reflect the dynamic change process of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the overall modeling flowchart of the present invention;

[0030] Figure 2 is the traditional steam turbine rotational speed control and protection system model referred to by the present invention;

[0031] Figure 3 This is the simplified model of the steam turbine speed control and protection system of the present invention;

[0032] Figure 4 This is the main steam valve model built for the simulation of the present invention;

[0033] Figure 5 This is the regulating valve model built for the simulation of the present invention;

[0034] Figure 6 This is the steam turbine model built for the simulation of the present invention;

[0035] Figure 7 This is the speed sensor model built for the simulation of the present invention;

[0036] Figure 8 This is the emergency stop valve model built for the simulation of the present invention;

[0037] Figure 9 This is the dispatching controller model built for the simulation of the present invention;

[0038] Figure 10 This is the dynamic result diagram of the normal start and stop control of the steam turbine (half opening) verified by the present invention;

[0039] Figure 11 This is the dynamic result diagram of the normal start and stop control of the steam turbine (fully open) verified by the present invention;

[0040] Figure 12 This is the dynamic result diagram of the steam turbine triggering the overspeed protection verified by the present invention. Detailed implementation manners

[0041] The present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments. Refer to Figure 1 the basic process shown. First, it is necessary to simplify the traditional model. Refer to Figure 2 , the traditional steam turbine speed control and protection system is mainly divided into two parts according to functions: speed control and protection. Among them, the speed control function is mainly achieved by the coordinated work of the starting device, the synchronizer, the intermediate amplifying mechanism, the servomotor and the steam distribution mechanism, and the protection function is achieved by the coordinated work between the speed sensor and the emergency stop system. Combining with the actual operation process of the steam turbine system, the thermal energy from the external steam is converted into mechanical energy, and then drives the motor to rotate to generate electric energy. In addition, further combining with the production process of the actual power plant, the above traditional model can be simplified into the system model shown in Figure 3 .

[0042] Refer to Figure 3As shown in the figure, the simplified model mainly consists of three parts, namely the main steam valve and the control valve responsible for realizing the speed control function, the speed sensor and the trip valve responsible for realizing the protection function, and the entity object to be controlled - the steam turbine.

[0043] To better illustrate the next modeling idea and main steps of the present invention, a simple introduction to timed automata is given first.

[0044] Timed automata is a kind of formal method. It adds clock variables on the basis of the original finite automata to simulate the logical clock that changes with the external time. The clock starts from 0 and grows synchronously with time. In timed automata, the time variable will participate in all stages of state transition, which not only solves the problem of poor real-time performance of the formal model, but also simplifies the description difficulty of real-time systems.

[0045] The model established by the present invention will follow the following definitions:

[0046] Definition 1: Timed automata. A timed automata system T is a six-tuple T = (S, S0, Σ, C, I, E), where:

[0047] (1) S is the set of all states that the system appears;

[0048] (2) S0 is the set of initial states of the system;

[0049] (3) ∑ is the set of triggering events for state transitions;

[0050] (4) C is the set of clocks of the system;

[0051] (5) I is a set of mapping relations. For each state subset s in the state set S, each state subset represents a state of the system, and for each state, a clock constraint can be found in the clock constraint set Φ(C) corresponding to it; <9000464>(6) is the set of state transition relations. Here, S and S′ represent the state sets of the system at different times. For example, there is such a set of transition relations (s, a, Φ, λ, s′), where s represents a certain state subset of S, s′ represents the state subset of S′, and λ represents the relevant clocks in the event set C that trigger the state transition. The above transition relation means that if the current state s is triggered by the event a and at the same time satisfies the clock constraint Φ, it will transfer from the s state to the s′ state. After the transfer ends, all the clocks in will be reset to wait for the next action.

[0053] Definition 2: Clock Constraint. For a set of clocks C, the set of clock constraints Φ(C) = {Φ | Φ is a clock constraint}, where Φ satisfies: Φ = x ≤ c | x ≥ c | x < c | x > c | Φ1 ∧ Φ2, where Φ1 and Φ2 are clock constraints, c is a constant, and x is the value of the set time variable.

[0054] It should be noted that for a state transition to occur, it is necessary not only to satisfy the occurrence of a certain triggering event but also to meet the clock constraint.

[0055] Returning to the system under study, as shown in Figure 3 . The time automaton method will be used to model the main steam valve, control valve, steam turbine, speed sensor, and emergency stop valve respectively, and finally, a synchronization signal will be set for synchronization.

[0056] The main steam valve has two functions. One is to control the steam, which is the power source of the system, to enter the steam turbine unit. The other is to prevent the steam from entering and block the steam turbine when the steam turbine finishes working or fails. Based on its basic working principle, the time automaton model of the main steam valve is obtained:

[0057] T m =(S m , S m0 , C, I, ∑ m , E m )

[0058] Generally speaking, the opening and closing commands of the main steam valve have a high degree of immediacy. Therefore, the influence of time constraints can be ignored, and the above formula can be simplified to:

[0059] T m =(S m , S m0 , ∑ m , E m )

[0060] where S m =(c m , s m ), c m represents the closed state of the main steam valve, and s m represents the open state of the main steam valve; S m0 =c m , and it is in the closed state when not working initially; ∑ m =(k m , g m , u), k m represents the issued opening command of the main steam valve, g m represents the issued closing command of the main steam valve, and u represents the emergency shutdown command of the main steam valve issued when a failure occurs; represents the state transition relationship of the main steam valve; It means that after the main steam valve receives the opening instruction, it transfers from the closed state to the open state; It means that after the main steam valve receives the closing instruction, it transfers from the open state to the closed state; It means that after the main steam valve receives the shut-off instruction, it transfers from the open state to the closed state.

[0061] The regulating valve is also called a control valve. In the steam turbine system, the steam turbine operates at different speeds by adjusting the opening degrees of different valves of the control valve. According to this principle, its model can be set as:

[0062] T a =(S a ,S a0 ,∑ a ,C,I,E a )

[0063] Similarly, ignoring the influence of time constraints, the above formula is simplified:

[0064] T a =(S a ,S a0 ,∑ a ,E a )

[0065] Among them, S a =(c a ,s h ,s a ), c a represents the closed state of the regulating valve, s h represents the open state (half opening) of the regulating valve, s a represents the open state (fully open) of the regulating valve; S a0 =c a , and it is in the closed state when it does not work initially; ∑ a =(k a ,k h ,g a ), k a represents the issued opening instruction (fully open) of the regulating valve, k h represents the issued opening instruction (half open) of the regulating valve, g a represents the issued closing instruction of the regulating valve; represents the state conversion relationship of the regulating valve; It means that after the regulating valve receives the fully open instruction, it transfers from the closed state to the fully open state; It means that after the regulating valve receives the half start instruction, it transfers from the closed state to the half open state; It means that after the regulating valve receives the closing instruction, it transfers from the fully open state to the closed state; It means that after the regulating valve receives the closing instruction, it transfers from the semi-start state to the closed state.

[0066] As the controlled object of the whole system, the steam turbine is a rotary steam power device, which is mainly responsible for converting the thermal energy in the steam into its own mechanical energy, driving the motor to rotate, and finally generating the electric energy sent to the outside world. The working state of the steam turbine is closely related to the state of each component in the speed control and protection system, and its state changes with the change of the state of these components. Based on this, the steam turbine model is constructed according to the timed automaton statements as follows:

[0067] T q =(S q , S q0 , ∑ q , E q )

[0068] Among them, S q =(c q , s t , s q ), c q represents the non-working state where the steam turbine speed is 0, s t represents the semi-open state of the steam turbine when the main steam valve is open but the regulating valve is not open (the speed is default 0 at this moment), s q represents the working state where the steam turbine starts to rotate after both the main steam valve and the regulating valve are open (the real-time speed is determined by the opening of the regulating valve); S q0 =c q , indicating that the steam turbine is initially in the non-working closed state; ∑ a =(k q , k t , k f , g h , g q , g u ), k q represents the synchronization signal sent to the steam turbine when the main steam valve is open, k t represents the synchronization signal sent to the steam turbine when the regulating valve is at half opening, k f represents the synchronization signal sent to the steam turbine when the regulating valve is fully open, g h represents the synchronization signal sent to the steam turbine when the regulating valve is normally closed, g q represents the synchronization signal sent to the steam turbine when the main steam valve is normally closed, g u represents the synchronization signal sent to the steam turbine when the main steam valve is emergently closed due to a running fault of the steam turbine; represents the state transition relationship of the steam turbine; represents that after the main steam valve of the steam turbine is open, it transfers from the non-working state to the semi-start state; It represents that, on the premise that the main steam valve of the steam turbine has been opened, after receiving the semi-opening or full-opening command of the control valve, it transfers to the starting state and rotates at a preset speed. It represents that the steam turbine transfers from the starting state to the semi-starting state after receiving the control valve closing signal; It represents that the steam turbine transfers from the semi-starting state to the non-operating state with a speed of 0 after receiving the main steam valve closing signal.

[0069] As a part of the protection system, the speed sensor works as a "supervisor" in the steam turbine system. It is responsible for monitoring the real-time speed of the steam turbine. When the speed exceeds the set threshold, the speed sensor acts and notifies the shutdown system to work, closing the main steam valve in time to stop the steam turbine. Based on this working principle, the timed automaton model of the speed sensor can be obtained:

[0070] T s =(S s , S s0 , ∑ s , E s )

[0071] Among them, S s =(slow, fast), slow represents the closed state of the speed sensor when the speed of the steam turbine is normal, and fas represents the alarm state of the speed sensor when the steam turbine is overspeed; S s0 =slow. When the system is not running, the speed of the steam turbine is 0 and the speed sensor is in the closed state; ∑ s ={|v|v > v max , v < max}}, ν represents the real-time speed of the steam turbine, and v max represents the threshold speed of the steam turbine; represents the state transition relationship of the speed sensor; represents that when the real-time speed of the steam turbine exceeds the threshold, the speed sensor transfers from the normal state to the alarm state when overspeed is detected. represents that when the real-time speed of the steam turbine is lower than the threshold, the speed sensor transfers back from the overspeed alarm state to the normal state.

[0072] Another component in the protection system - the shutdown valve often participates in the protection action as an "executor". When the system is running normally, it is in the closed state; once an abnormality occurs in the system, it will transfer to the working state, shutting off all the intake valves to make the steam turbine stop safely and protect the steam turbine from damage. The shutdown valve is optimized into the following model:

[0073] T u =(S u , S u0 , Σ u , Eu )

[0074] Among them, S u =(c u , s u ), c u represents the closed state of the shut-off valve, and s u represents the open state of the shut-off valve; S u0 =c u , and it is in the closed state when not working initially; ∑ u =(k u , g u ), k u represents the open command of the shut-off valve sent after the speed sensor detects an abnormality, and g u represents the closed command of the shut-off valve after the steam turbine system stops; represents the state transition relationship of the shut-off valve; represents that after the shut-off valve receives the abnormality command reported by the speed sensor, the shut-off valve transfers from the closed state to the open state; represents that after the shut-off valve receives the shutdown command, the shut-off valve transfers from the open state to the closed state.

[0075] So far, the creation of the individual models of the important components in the entire steam turbine speed control and protection system is completed. Next, use the characteristics of the product of automata to integrate the above models.

[0076] Definition 3: Product integration. Let T a , T b be two automata models. Among them, T a =(S a , S a0 , ∑ a , E a ), T b =(S b , S b0 , ∑ b , E b ); then the product of the two can be expressed as another automata model:

[0077]

[0078] Among them, S a , S b represent the state sets of the two timed automata T a , T b respectively; S a0 , S b0 represent the initial state sets of the two timed automata T a , T b respectively; ∑ a , ∑ b represent Ta , T b The set of triggering events of two timed automata; E a , E b respectively represent T a , T b The set of state transitions of two timed automata; S x = S a ∪ S b represents the state set of the new timed automaton, which is T a , T b the union of the states of two timed automata; S x0 = S a0 ∪ S b0 represents the initial state set of the new timed automaton, which is T a , T b the union of the initial states of two timed automata; ∑ x represents the set of transition conditions, and the synchronous signals in the sets of triggering events of T a , T b two timed automata can be omitted to obtain; E x is the transition relation, which needs to be solved according to the transition conditions.

[0079] Therefore, the overall model of the speed control protection system can be obtained:

[0080] T A = (S A , S A0 , ∑ A , E A )

[0081] Among them, the initial state set S A0 is:

[0082] S A0 = (c m , c a , c q , slow, c u )

[0083] The state set S A is:

[0084] S A = {S A0 , S A1 , S A2 , S A3 , S A4 , S A5 , S A6 , S A7}

[0085] Here, S A1 , SA2 , S A3 , S A4 , S A5 , S A6 , S A7 respectively represent the semi-start state, semi-opening start state, full-opening start state, overspeed alarm state, shut-off state, deceleration state, and semi-closed state of the system.

[0086] SA 1 = (s m , c a , s t , slow, c u );

[0087] S A2 = (s m , s h , s q , slow, c u );

[0088] S A3 = (s m , s a , s q , slow, c u );

[0089] S A4 = (s m , c a , s t , fast, c u );

[0090] S A5 = (s m , s a , s q , fast, s u );

[0091] S A6 = (c m , c a , c q , fast, s u );

[0092] S A7 = (c m , c a , c q , slow, s u ).

[0093] Omit the synchronization signal k in the system q , k t , k f , g h , gq After that, the event trigger set ∑ is obtained A as follows:

[0094] ∑ A =(k m , k a , k h , k u , u, g u , g a , g m , v > v max , v < v max )

[0095] The state transition set E A is as follows:

[0096] E A ={δ1, δ2, δ3, δ4, δ5, δ6, δ7, δ8, δ9, δ 10 , δ 11}

[0097] Here, represents that after the main steam valve is opened, the system transfers from the initial state to the semi-start state; represents that after the regulating valve is opened at half opening, the system transfers from the semi-start state to the semi-opening start state; represents that after the regulating valve is opened fully, the system transfers from the semi-start state to the full-opening start state; represents that after the regulating valve is closed, the system transfers from the semi-opening start state to the semi-start state; represents that after the regulating valve is closed, the system transfers from the full-opening start state to the semi-start state; represents that after the main steam valve is closed, the system transfers from the semi-start state to the initial state; represents that when the steam turbine is overspeed, the system transfers from the start state to the overspeed alarm state; represents that after the emergency stop valve is opened, the system transfers from the overspeed alarm state to the emergency stop state; represents that after the main steam valve is emergently shut off, the system transfers from the emergency stop state to the deceleration state; represents that after the steam turbine speed is lower than the detection threshold, the system transfers from the deceleration state to the semi-closed state; and represents that after the emergency stop valve is closed, the system transfers from the semi-closed state to the initial state.

[0098] Next, the model of the present invention is verified and described in combination with the UPPAAL simulation software.

[0099] In the present invention, the above-mentioned timed automaton model will be created using the UPPAAL software, and three experimental processes will be simulated. Experiment 1 will simulate the normal start-stop process of the steam turbine under the condition of half-open regulating valves; Experiment 2 will simulate the normal start-stop process of the steam turbine under the condition of fully open regulating valves; Experiment 3 will simulate the working process of the steam turbine protection system under overspeed conditions.

[0100] Before conducting the following experiments, it is necessary to first construct a simulation model in the UPPAAL software editing interface. Refer to Figure 4 the main steam valve model, Figure 5 the regulating valve model, Figure 6 the steam turbine model, Figure 7 the rotational speed sensor model, and Figure 8 the emergency stop valve model. They are synchronized in time through synchronization signals with each other. In addition, an opening controller as shown in Figure 9 is set to change the opening of the regulating valve.

[0101] The basic states of the above-mentioned models referred to in the figure are shown in the following table.

[0102] Table 1 Model State Table

[0103]

[0104] The basic parameters of the above-mentioned models referred to in the figure are shown in the following table.

[0105] Table 2 Model Parameter Variable Table

[0106]

[0107]

[0108] Experiment 1: Start-stop Process of the Steam Turbine with Half-open Regulating Valves

[0109] In this experiment, the process of opening and closing the main steam valve and the regulating valve is simulated by setting the values of different parameter variables. The specific parameter settings are shown in the following table:

[0110] Table 3 Parameter Variable Table for the Start Process with Half-open Regulating Valves

[0111]

[0112] The closing process is carried out on the basis of the start of the steam turbine. For the integrity of the simulation results, when the state of the steam turbine transfers to the start state, a shutdown command will be directly issued.

[0113] Table 4 Parameter Variable Table for the Stop Process with Half-open Regulating Valves

[0114]

[0115] After the parameter settings are completed, enter the simulator interface of the UPPAAL software for process simulation. According to the dynamic simulation results Figure 10 As shown, it can be seen that after the valve opening command is issued, the main steam valve and the regulating valve will open in sequence, and a valve opening synchronization signal will be sent to the steam turbine; after receiving the valve opening synchronization signal, the steam turbine will start to rotate slowly. Subsequently, after the steam turbine starts, since the shut-off command is issued immediately, as the regulating valve and the main steam valve close, the steam turbine will slowly stop until the rotational speed is 0.

[0116] Experiment 2: Full-open degree start-stop process of the steam turbine

[0117] The main difference between this experiment and Experiment 1 is that the opening degree of the regulating valve is different, which will result in different rotational speeds of the steam turbine after startup. Therefore, only the opening degree command of the regulating valve needs to be changed, and the other commands remain unchanged. The specific parameter settings are as follows:

[0118] Table 5 Parameter variable table for full-open degree startup process

[0119]

[0120] After the parameter settings are completed, enter the simulator interface of the UPPAAL software for process simulation. According to the dynamic simulation results Figure 11 As shown, except for the different opening degrees of the regulating valve, the dynamic processes of the full-open degree and half-open degree models are basically the same.

[0121] Experiment 3: Overspeed protection process of the steam turbine

[0122] In this experiment, the functionality of the protection system will be verified. It should be noted that the set rotational speed threshold is 3300 revolutions. The specific parameter settings are as follows:

[0123] Table 6 Parameter variable table for overspeed protection process

[0124]

[0125] After the parameter settings are completed, enter the simulator interface of the UPPAAL software for process simulation. According to the dynamic simulation results Figure 12 As shown, it can be seen that when the steam turbine starts normally, the rotational speed sensor detects that the real-time rotational speed of the steam turbine exceeds the set threshold and alarms the trip valve; the trip valve enters the startup state, closes the main steam valve, and the steam turbine stops emergently.

[0126] It can be seen from the experiments that the new steam turbine control speed protection system model proposed by the present invention effectively depicts the implementation process of the control and protection logic of the steam turbine speed control protection system; at the same time, due to its own immediacy, it can more completely reflect the dynamic working process of the system. It well solves the problem that the traditional model cannot describe the transfer of various operating conditions of the steam turbine and the operation processes of various types of equipment under each operating condition.

Claims

1. A modeling method for a steam turbine speed control and protection system based on timed automata, characterized in that, including Set up the speed control and protection system model of the steam turbine: including the main steam valve, which is used to control the steam entering and leaving the system; The regulating valve is used to adjust the speed of the steam turbine; the speed sensor is used to detect whether the steam turbine is overspeed; the shut-off valve is used to urgently close the main steam valve when the steam turbine is overspeed; the steam turbine is used to convert the steam heat energy into mechanical energy, drive the motor to rotate, and generate electric energy; Establish a model of the steam turbine speed control protection system: T A =(S A , S A0 , ∑ A , E A ) Among them, S A0 is the set of initial states: S A0 = (c m , c a , c q , slow, c u ) Among them, c m , c a , c q , slow, c u respectively represent the main steam valve closed state, the control valve closed state, the turbine closed state, the normal speed state of the speed sensor, and the emergency stop valve closed state; S A is the set of states; S A = {S A0 , S A1 , S A2 , S A3 , S A4 , S A5 , S A6 , S A7} Among them, S A1 , S A2 , S A3 , S A4 , S A5 , S A6 , S A7 respectively represent the semi-start state, semi-opening start state, full-opening start state, overspeed alarm state, trip state, deceleration state and semi-closed state of the system; S A1 = (s m , c a , s t , slow, c u ); S A2 = (s m , s h , s q , slow, c u ); S A3 =(s m ,s a ,s q ,slow,c u ); S A4 =(s m ,c a ,s t ,fast,c u ); S A5 =(s m ,s a ,s q ,fast,s u ); S A6 =(c m ,c a ,c q ,fast,s u ); S A7 = (c m , c a , c q , slow, s u ); where s m represents the opening state of the main steam valve; s t represents the semi - opening state of the steam turbine; s q represents the starting state of the steam turbine; s h represents the semi - opening state of the control valve; s a represents the fully - opening state of the control valve; s u represents the opening state of the emergency stop valve; c u represents the closing state of the emergency stop valve; fast represents the overspeed alarm state of the speed sensor; ∑ A is the event trigger set; ∑ A =(k m ,k a ,k h ,k u ,u,g u ,g a ,g m ,v>v max ,v<v max ) where k m represents the main steam valve opening command; k a represents the regulating valve half-opening command; k h represents the regulating valve full-opening command; k u represents the emergency stop valve opening command; u represents the emergency stop main steam valve command issued by the emergency stop valve; g u represents the emergency stop valve closing command; g a represents the regulating valve closing command; g m represents the main steam valve closing command; v max represents the speed threshold of the steam turbine; v > v max represents the steam turbine speed overspeed; v < v max represents the normal steam turbine speed; E A is the state transition set; E A = {δ1, δ2, δ3, δ4, δ5, δ6, δ7, δ8, δ9, δ 10 , δ 11} Among them, represents that after the main steam valve is opened, the system transfers from the initial state to the semi-start state; represents that after the regulating valve is opened to half opening, the system transfers from the semi-start state to the semi-opening start state; represents that after the regulating valve is opened to full opening, the system transfers from the semi-start state to the full-opening start state; represents that after the regulating valve is closed, the system transfers from the semi-opening start state to the semi-start state; represents that after the regulating valve is closed, the system transfers from the full-opening start state to the semi-start state; represents that after the main steam valve is closed, the system transfers from the semi-opening start state to the semi-start state; represents that when the steam turbine is overspeed, the system transfers from the full-opening start state to the overspeed alarm state; represents that after the emergency stop valve is opened, the system transfers from the overspeed alarm state to the emergency stop state; represents that after the main steam valve is emergently shut off, the system transfers from the emergency stop state to the deceleration state; represents that after the steam turbine speed is lower than the detection threshold, the system transfers from deceleration to the semi-closed state; and represents that after the emergency stop valve is closed, the system transfers from the semi-closed state to the initial state.

2. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 1, formalize the modeling of the speed control and protection system of the steam turbine, including the following processes: Establish the timed automata model of the main steam valve and simplify it by ignoring the time constraints; Establish the timed automata model of the regulating valve and simplify it by ignoring the time constraints; Establish the timed automata model of the steam turbine and simplify it by ignoring the time constraints; Establish the timed automata model of the speed sensor and simplify it by ignoring the time constraints; Establish the timed automata model of the shut-off valve and simplify it by ignoring the time constraints; Integrate the main steam valve, governing valve, speed sensor, emergency stop valve and steam turbine into the steam turbine speed control and protection system model T using the integral product A .

3. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 2, the timed automata model of the main steam valve is established as: T m = (S m , S m0 , ∑ m , E m ) Among them, S m ,S m0 ,∑ m ,E m respectively represent the state set of the main steam valve, the initial state, the trigger time set, and the state transition set.

4. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 2, the timed automata model of the regulating valve is established as: T1 = (S a , S a0 , ∑ a , E a ) Among them, S a , S a0 , ∑ a , E a respectively represent the state set, initial state, trigger time set and state transition set of the regulating valve.

5. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 2, the timed automata model of the steam turbine is established as: T q = (S q , S q0 , ∑ q , E q ) Among them, S q , S q0 , ∑ q , E q represent the state set, initial state, trigger time set and state transition set of the steam turbine, respectively.

6. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 2, the timed automata model of the speed sensor is established as: T s = (S s , S s0 , ∑ s , E s ) Among them, S s , S s0 , ∑ s , E s respectively represent the state set of the rotational speed sensor, the initial state, the trigger time set, and the state transition set.

7. According to the method for modeling the speed control and protection system of the steam turbine based on timed automata described in claim 2, the timed automata model of the shut-off valve is established as: T u = (S u , S u0 , ∑ u , E u ) Among them, S u , S u0 , ∑ u , E u respectively represent the state set of the shut-off valve, the initial state, the trigger time set, and the state transition set.

8. The modeling method of the steam turbine speed control and protection system based on timed automata according to claim 2, uses integration product to obtain the steam turbine speed control and protection system model T A , wherein, The integration method is: Let T a , T b be two timed automaton models, T a =(S a ,S a0 ,∑ a ,E a ),T b =(S b ,S b0 ,∑ b ,E b ) Among them, S a , S b respectively represent the state sets of a , T b two timed automata; S a0 , S b0 respectively represent the initial state sets of a , T b two timed automata; ∑ a , ∑ b respectively represent the trigger event sets of a , T b two timed automata; E a , E b respectively represent the state transition sets of a , T b two timed automata; Using the integration product, a new timed automata model can be obtained as: Among them, S x = S a ∪ S b represents the state set of the new timed automaton, which is T a , T b the union of the states of the two timed automata; S x0 = S a0 ∪ S b0 represents the initial state set of the new timed automaton, which is T a , T b the union of the initial states of the two timed automata; ∑ x represents the set of transition conditions. By omitting the synchronization signals in the trigger event sets of T a , T b the two timed automata, it can be obtained; E x is the transition relation and needs to be solved according to the transition conditions.

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