A precise compensation control method suitable for coupling storage system

Abstract

The application discloses a kind of precision compensation control methods suitable for coupling storage system, comprising: 1) based on the material and energy balance of coupling storage system, establish the general form of coupling storage system mechanism model;2) based on the general form of coupling storage system mechanism model, construct the precision compensation control signal to system state set point change;3) based on the general form of coupling storage system mechanism model, construct the precision compensation control signal to system output set point change;4) comprehensive consideration precision compensation control signal of system state and output, construct precision compensation control method suitable for coupling storage system, realize the precision compensation control of coupling storage system.The application gives the general form of coupling storage system mechanism model, applicable to all material and energy balance systems.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of industrial process control, and relates to a precise compensation control method suitable for a coupled storage system. BACKGROUND

[0002] In industrial process control, there are a large number of coupled storage systems, from small volume systems storing substances to large generator sets storing energy. In theory, as long as there is a volume, there is a phenomenon of storing substances or energy. Whether the system stores substances or energy, they have two common characteristics: 1) the inertia of the system is related to the storage coefficient, the larger the storage coefficient, the longer the inertia time of the system, and the more difficult it is to apply effective control force; 2) there is a serious coupling relationship between the input and the output of the system, and the input needs to be first reflected in the state of the system to further affect the output.

[0003] These two characteristics of the storage system fully reflect its large inertia and strong coupling characteristics. The "instant" control method based on the traditional PID algorithm is difficult to obtain good control effect, and the advanced control algorithm based on the model is strongly dependent on the model. It is of great significance to study the mass and energy balance principle of the storage system and construct a precise compensation control method suitable for the coupled storage system from the mechanism level. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a precise compensation control method suitable for a coupled storage system from the mechanism level based on the mass and energy balance principle of the storage system. The method gives a general form of the mechanism model of the coupled storage system, which is suitable for all mass and energy balance systems.

[0005] The present application is realized by adopting the following technical solutions:

[0006] A precise compensation control method suitable for a coupled storage system, comprising the following steps:

[0007] 1) based on the mass and energy balance of the coupled storage system, a general form of the mechanism model of the coupled storage system is established;

[0008] 2) based on the general form of the mechanism model of the coupled storage system, a precise compensation control signal for the change of the system state set point is constructed;

[0009] 3) based on the general form of the mechanism model of the coupled storage system, a precise compensation control signal for the change of the system output set point is constructed;

[0010] 4) considering the precise compensation control signals of the system state and the output, a precise compensation control method suitable for the coupled storage system is constructed to realize the precise compensation control of the coupled storage system.

[0011] The further improvement of the present application is that the general form of the coupling storage system mechanism model is:

[0012]

[0013] In the formula, C is the storage coefficient, X is the system state, U is the system input, and Y is the system output.

[0014] The further improvement of the present application is that the precise compensation control signal for the change of the system state set point is:

[0015]

[0016] In the formula, ΔU1 is the compensation amount for the change of the system state set point per unit time; C is the storage coefficient; X sp is the system state set point.

[0017] The further improvement of the present application is that the precise compensation control signal for the change of the system output set point is:

[0018]

[0019] In the formula, ΔU2 is the compensation amount for the change of the system output set point per unit time; C is the storage coefficient; Y sp is the system output set point; K is the ratio of the change amount of the system state process value to the change amount of the system output set point when the system state is in open loop control and the system output is in closed loop control:

[0020]

[0021] In the formula, ΔX pv is the change amount of the system state process value, and ΔY sp is the change amount of the system state set point.

[0022] The further improvement of the present application is that K is related to the closed loop control parameter of the system output in addition to the characteristics of the system itself, so the system and the closed loop control loop of the system output are regarded as a generalized object according to the actual object, and are tested and obtained.

[0023] The further improvement of the present application is that the precise compensation control signal suitable for the coupling storage system is to superimpose the compensation control signals:

[0024]

[0025] The present application has at least the following beneficial technical effects:

[0026] 1. The application provides a precise compensation control method for a coupled storage system, which can realize precise compensation for the state and output set point changes of the coupled storage system.

[0027] First, according to step 1), the established mechanism model of the coupled storage system has large inertia and strong coupling characteristics, which is a common difficult-to-control object in industrial control processes. The inertia of the model is reflected on the storage coefficient C, and the larger the storage coefficient C, the longer the inertia time of the system; the strong coupling characteristics of the model are reflected between the system state X and the output Y, which influence each other in actual control.

[0028] Second, for the difficult-to-control problem of the coupled storage system in step 1), the application innovatively constructs precise compensation control signals ΔU1 and ΔU2 for the set point changes of the system state X and the output Y in steps 2) and 3), both of which fully consider the mechanism characteristics of the storage system, i.e. the storage coefficient C, and also ingeniously cover the change trend of the system state X and the output Y set point, which can realize precise compensation for the set point changes of the system state X and the output Y.

[0029] 2. The mechanism model of the coupled storage system is established based on system mass or energy balance, which can be applied to all mass balance and energy balance systems. The storage coefficient C is a key parameter that affects the control performance of the storage system, and there is also a coupling relationship between the system state X and the output Y, which leads to the difficult-to-control problem of the coupled storage system.

[0030] 3. The precise compensation control signal for the set point change of the system state is obtained by taking the change trend of the system state set point and multiplying the storage coefficient C, which can realize precise compensation for the set point change of the system state.

[0031] 4. The precise compensation control signal for the set point change of the system output is obtained by taking the change trend of the system output set point , multiplying the storage coefficient C, and converting to the dimension of the system state X using K, which can realize precise compensation for the set point change of the system output.

[0032] 5. Superimposing the given precise compensation control signals can realize precise compensation for the set point changes of the system state X and the output Y. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The structure diagram of a typical mass balance storage system-single tank.

[0034] Figure 2 The schematic diagram of the water flow set point change test scheme.

[0035] Figure 3Set point change test curve for outlet flow.

[0036] Figure 4 Schematic diagram of precise compensation control scheme for single-tank storage system.

[0037] Figure 5 Curve of each control variable and controlled variable.

[0038] Figure 6 Schematic diagram of generation process of inlet valve opening degree instruction. DETAILED DESCRIPTION

[0039] A single-tank water tank is a typical material balance storage system. The present application is further described in detail below by taking a single-tank water tank as an example. The description is an explanation of the present application and not a limitation.

[0040] The present application is a precise compensation control method suitable for coupled storage systems. Taking a single-tank water tank as an example (as shown in the figure) : Figure 1

[0041] (1) Establish a storage model of the water tank system

[0042] Based on the general form of the storage system model, a mass balance model of the single-tank water tank is established:

[0043]

[0044] In the formula, D i is the inlet flow of the system, kg / s; D o is the outlet flow of the system, kg / s; h is the liquid level state of the system, m; C S is the storage coefficient of the water tank system, kg / m.

[0045] It is assumed that the inlet flow is proportional to the inlet valve opening degree, and there is a certain delay time between the change of the inlet valve opening degree and the change of the inlet flow due to the long inlet pipeline. Therefore, the inlet flow of the water tank system is:

[0046] D i = k i u i e -τs (2)

[0047] In the formula, k i is the inlet valve-flow coefficient; u i is the inlet valve opening degree, %; τ is the delay time between the change of the inlet valve opening degree and the change of the inlet flow, s.

[0048] It is assumed that the outlet flow is proportional to the arithmetic square root of the outlet valve cross-sectional area and the water tank liquid level height. Therefore, the outlet flow of the water tank system is:

[0049] ​

[0050] where c p Density of water, c p = 1000 kg / m 3 ; A o Cross-sectional area of outlet valve, m 3 ; u o Opening of outlet valve, %; g is the acceleration of gravity, g = 10 m / s 2 .

[0051] Based on the above, the storage model of the water tank system is:

[0052]

[0053] (2) Determine the unknown parameters of the water tank model

[0054] Assume that the water tank is cylindrical, the bottom radius r = 0.4 m; the tank height H0 = 1 m; the outlet valve cross-sectional area A o = 0.002 m 2 ; the initial opening of the outlet valve u o = 50%, the initial liquid level state H = 0.8 m; the initial inlet valve opening u i = 50%, the inlet valve opening changes to the delay time τ = 50 s of the inlet water flow change.

[0055] At steady state, the water tank outlet flow is equal to the inlet flow, so the inlet valve flow coefficient k i can be calculated according to formula (5). At the same time, the water tank storage coefficient can be calculated according to formula (6) according to the definition.

[0056]

[0057]

[0058] After calculation, k i = 8; the water tank storage coefficient C S = 502.4 kg / m.

[0059] Substitute the above model parameters to form the water tank storage system model:

[0060]

[0061] (3) Precise compensation control of the water tank system

[0062] Considering that the actual input and output of the system are valve openings, in order to facilitate the design of precise compensation control, formula (7) is rewritten as:

[0063]

[0064] Precise compensation for water tank system liquid level state change:

[0065]

[0066] Precise compensation for water tank system water outlet flow change:

[0067] In order to obtain the characteristic parameter K of the water tank system, the present application designs a water outlet flow set point change test system diagram for the above water tank system, as shown in Figure 2

[0068] As can be seen from the figure, the test system contains two control loops, wherein the liquid level control adopts an open loop mode, feeding forward a proper water inlet valve opening degree through the water outlet flow set point, and the feedforward control coefficient The water outlet flow adopts PID closed loop control, and the PID1 controller parameters are K P = 3 and K I = 2. The test results are shown in Figure 3

[0069] Through testing, when the water outlet flow set point changes, the water storage or release coefficient

[0070] Therefore, the precise compensation amount for the water outlet flow change of the water tank is:

[0071]

[0072] Adding formula (9) and formula (10) together, it can be known that the precise compensation control for the typical water tank system is:

[0073]

[0074] (4) Overall control scheme

[0075] Figure 4 The precise compensation control scheme of the single-tank storage system is given. As can be seen from the figure, the strategy mainly includes water outlet flow control and water tank liquid level control.

[0076] Since the response rate of the water outlet valve opening degree change to the water outlet flow is fast, the present application directly adopts feedback control based on the PID algorithm to complete it in the implementation process, and the PID1 parameters are: proportional gain K P = 3 and integral gain K I = 2;

[0077] ​​Because of the big delay and inertia between the valve opening and the water level, the feedforward-feedback control is used, in which the feedforward control contains two parts: 1) static feedforward (FF1) based on the change of the outlet flow set point; 2) accurate compensation feedforward (FF2) based on the water level state and the change of the outlet flow set point. The parameters of the feedback part PID2 are: proportional gain K P = 3, integral gain K I = 0.001.

[0078] Note that the feedback control has a switch, when it is switched to 0, it is equivalent to the control in open loop mode, when it is switched to PID, it is equivalent to the control in closed loop mode, which is mainly to verify that the accurate compensation control can basically achieve accuracy in theory (see simulation verification for details).

[0079] (5) Simulation verification

[0080] In order to verify the effectiveness of the accurate compensation control of the single-tank storage system, the water level open loop control mode and the closed loop control effect are simulated and compared in the implementation process (superscript: 1 represents that the control mode is switched to the open loop mode in Figure 4 , 2 represents that the control mode is switched to the closed loop mode in Figure 4 ), the results are shown in Figure 5 and Figure 6 .

[0081] Figure 5 The curves of the control variables and the controlled variables are given. As can be seen from the figure, in the water level open loop mode, the accurate compensation control based on the water tank storage system can make the water level state follow the set point well, but as can be seen from the amplification part, there is a static deviation between it and the closed loop control part, so when the closed loop control mode is switched in, the static deviation of the water level is significantly reduced.

[0082] Figure 6 The generation process of the water tank inlet valve opening command is given. As can be seen from the figure, whether the water level control is in open or closed loop, the accurate compensation control FF2 of the water tank storage system is coincident, the difference is that in the water level feedback control, the closed loop control produces a certain feedback adjustment, but its amplitude is small, the main reason is that the accurate compensation control can follow the water level state set point well.

Claims

1. A precise compensation control method adapted to coupled storage systems, characterized in that, Includes the following steps: 1) Based on the material and energy balance of the coupled storage system, the general form of the mechanism model of the coupled storage system is established as follows: In the formula, C is the storage coefficient, X is the system state, U is the system input, and Y is the system output; 2) Based on the general form of the coupled storage system mechanism model, a precise compensation control signal for changes in the system state setpoint is constructed as follows: In the formula, C is the compensation amount for the change in the system state setpoint per unit time; C is the storage coefficient. System state setpoint; 3) Based on the general form of the coupled storage system mechanism model, a precise compensation control signal for changes in the system output setpoint is constructed as follows: In the formula, C is the compensation amount for the change in the system output setpoint per unit time; C is the storage coefficient. K is the system output setpoint; K is the ratio of the change in the system state process value to the change in the system output setpoint when the system output is under closed-loop control and the system state is under open-loop control. 4) Taking into account both the system state and the precise compensation control signal of the output, a precise compensation control method adapted to the coupled storage system is constructed to achieve precise compensation control of the coupled storage system; the precise compensation control signal adapted to the coupled storage system is the superposition of compensation control signals, and the specific expression is as follows: 。 2. The precise compensation control method adapted to a coupled storage system according to claim 1, characterized in that, The expression for K is as follows: In the formula, The change in the system state process value. The change in the system state setpoint.

3. The precise compensation control method adapted to a coupled storage system according to claim 1, characterized in that, In addition to being related to the characteristics of the system itself, K is also related to the closed-loop control parameters of the system output. Therefore, based on the actual object, the system and its output closed-loop control loop are regarded as a generalized object and obtained through experimental testing.

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