Three-phase electrode current preset time intelligent loop control method for electric smelting magnesium furnace

Abstract

The invention discloses a three-phase electrode current preset time intelligent loop control method for an electric smelting furnace for magnesia, which specifically comprises the following steps: 1) selecting the electric smelting furnace for magnesia as a research object and analyzing the characteristics of equipment, and taking the electric smelting furnace as a representative as the production index of the smelting process of major energy-consuming equipment in the smelting process, namely the electric energy consumed by each ton of qualified products, namely the unit energy consumption; (2) controlled objects of a control system of the electrical smelting furnace for magnesium comprise unit energy consumption of the electrical smelting furnace for magnesium and three-phase electrode current of the electrical smelting furnace for magnesium, the controlled quantity is the rotating speed and direction of a three-phase dragging motor of the electrical smelting furnace for magnesium, and the unit energy consumption of a product is directly influenced by the magnitude and the stability degree of the three-phase electrode current value in the smelting process; and (3) analyzing the relationship between the three-phase electrode current of the electric smelting magnesium furnace and the rotating speed of the three-phase dragging motor, and calculating the rotating speed of the three-phase dragging motor according to the deviation between the actual three-phase electrode current value and the three-phase electrode current set value under the heating and melting working condition. A preset time consistency control algorithm based on self-adjusting gain is adopted to obtain the rotating speed and direction of the three-phase dragging motor under the heating and melting working condition; and (4) adjusting parameters of the preset time consistency control scheme in the step (3), performing preset time algorithm verification, and performing corresponding comparison with a PID algorithm of a traditional control method.

Description

Technical Field

[0001] The present invention relates to the field of complex industrial process control, and in particular to a preset time intelligent control method based on major energy-consuming equipment, in particular to a preset time intelligent loop control method for three-phase electrode current of an electric magnesium furnace. Background Art

[0002] Frequent changes in raw materials, dramatic fluctuations in working conditions, and complex and continuous challenges in the production process in industrial production have led to production management decisions being highly dependent on human experience and knowledge, making it difficult to adapt to rapidly changing production conditions, and limiting the flexibility and efficiency of industrial development. Therefore, innovative technologies and methods are urgently needed to optimize the production process and improve the accuracy and response speed of decision-making.

[0003] In the industrial field, the efficient operation of major energy-consuming equipment is crucial to achieving energy conservation and emission reduction. However, since the controlled object characteristics, control objectives, constraints, design scope and system implementation structure of major energy-consuming equipment far exceed the scope of application of existing control theories and control system design methods, so far, the world has not yet formed a theory and system design method to achieve the optimization and control of the entire process of high-energy-consuming equipment production and manufacturing. Summary of the invention

[0004] Based on the above-mentioned background technology problems, the present invention targets major energy-consuming equipment with comprehensive complexity, represented by electric magnesium furnaces, and combines a preset time control algorithm to achieve satisfactory coordination between system rapidity and stability, thereby ensuring safe, stable and optimized operation of the production process.

[0005] The present invention studies the design method of intelligent control systems with high dynamic performance, and realizes intelligent operation optimization of the production process and significant reduction of energy consumption per ton for major energy-consuming equipment such as electric magnesium furnaces. Complex industrial processes require that the output of the controlled object track the loop set value as well as possible during the production process. Once the tracking error exceeds the allowable range by too much, abnormal operating conditions will occur. The preset time control method is designed so that the output of the controlled object can quickly track the changing set value, and the tracking error can always be controlled within the allowable range during operation, so as to achieve a satisfactory coordination between the rapidity and stability of the system, thereby ensuring safe, stable and optimized operation of the production process. The specific steps are as follows:

[0006] (1) Step 1: Select the electric fused magnesium furnace as the research object and analyze the equipment characteristics. The production index of the smelting process of major energy-consuming equipment represented by the electric fused magnesium furnace is the electric energy consumed per ton of qualified products, that is, the unit energy consumption.

[0007] (2) Step 2: The controlled objects of the electric fused magnesium furnace control system include the unit energy consumption of the electric fused magnesium furnace and the three-phase electrode current of the electric fused magnesium furnace. The controlled quantity is the rotation speed and direction of the three-phase traction motor of the electric fused magnesium furnace. The unit energy consumption of the electric fused magnesium furnace during the smelting process is directly affected by the size and stability of the three-phase electrode current value.

[0008] (3) Step 3: Analyze the relationship between the three-phase electrode current of the electric magnesium furnace and the rotation speed of the three-phase drive motor. According to the deviation between the actual three-phase electrode current value and the set value of the three-phase electrode current under the heating and melting conditions, a preset time consistency control algorithm based on self-regulating gain is used to obtain the speed and direction of the three-phase drive motor under the heating and melting conditions.

[0009] (4) Step 4: Adjust the parameters of the preset time consistency control scheme in step 3, verify the preset time algorithm and compare it with the traditional control method PID algorithm.

[0010] According to the electric fused magnesium furnace three-phase electrode current preset time intelligent loop control method of the present invention, in step one, the following steps are included:

[0011] The electric energy consumption in the smelting process of the electric fused magnesium furnace is huge. The unit energy consumption index used to reflect the energy efficiency of the product can be calculated by the following formula:

[0012]

[0013] Among them, r represents the unit energy consumption of the electric fused magnesium furnace, E represents the total electric energy consumed in a complete smelting process of the electric fused magnesium furnace, and m represents the total output of qualified products obtained after a complete smelting process of the electric fused magnesium furnace. In order to reduce energy consumption, the control target of the smelting process of the electric fused magnesium furnace is to control the unit energy consumption of the product within the target value range and as small as possible under the condition of meeting the production constraint in advance. That is,

[0014]

[0015] in Indicates the lower limit of the output of the fused magnesium furnace. and They represent the upper and lower limits of the unit energy consumption of the fused magnesium furnace respectively. The target value of unit energy consumption of electric fused magnesium furnace is r * The allowable fluctuation range.

[0016] According to the electric fused magnesium furnace three-phase electrode current preset time intelligent loop control method of the present invention, in step 2, the following steps are included:

[0017] The controlled objects of the electric magnesium furnace control system include the unit energy consumption r of the product and the three-phase electrode current y j (t), j = 1, 2, 3, the control quantity is the rotation speed and direction ±u of the three-phase traction motorj (t); where r and y j The expressions of (t) are:

[0018] r=f1(y j (t),S L ,B1,B2,B3,B4,B5,m)

[0019] y j (t) = f2(B1, B2, B3, B4, B5, h n ,ρ m.A ,ρ m.B ,h m ,ρ n ,r0,l)

[0020]

[0021] Δy j (t)≤Δy max

[0022] u min <|u j (t)|≤u max (3)

[0023] Where f1(·) is an unknown nonlinear function describing the relationship between the unit energy consumption r of the fused magnesium furnace and its influencing factors, r and the three-phase electrode current value y j (t), current smelting condition S L , melting voltage B1, electrode diameter B2, furnace diameter B3, raw material particle length B4, raw material impurity composition B5 and product output m parameters; f2(·) is the parameter describing the three-phase electrode current y j (t) is an unknown nonlinear function of the relationship between it and its influencing factors, y j (t) and boundary conditions B1, .., B5, layer thickness h n 、Arc resistivity ρ m.A 、Resistivity of molten pool ρ m.B , molten pool depth h m , material layer resistivity ρ n , the spherical radius r0 of the electrode end and the electrode spacing l; I min and I max Respectively represent the three-phase electrode current setting values The upper and lower limits of i=1, ···, 3 represent the three-phase electrode current setting values ​​under the three working conditions of heating and melting, feeding and exhausting respectively; Δy j (t) represents the rate of change of the three-phase electrode current, Δy max Indicates the upper limit of the current change rate; u min and u max Respectively represent the control quantity uj (t) upper and lower limits; during the smelting process, when the three-phase electrode current can stably track the appropriate current setting value, the furnace temperature is guaranteed to be maintained within the range of 2750℃-2850℃, thereby controlling the energy consumption per ton within a certain indicator.

[0024] According to the electric fused magnesium furnace three-phase electrode current preset time intelligent loop control method of the present invention, in step three, the following steps are included:

[0025] During the smelting process, the electrode voltage is fixed, and the dynamic characteristics of the three-phase electrode current and the corresponding arc resistance near the working point of the electric magnesium furnace show linear characteristics:

[0026]

[0027] where k y is the current coefficient, and V0(t) is a bounded unmodeled dynamic term. Arc resistance With arc length L j is proportional to each other, that is:

[0028]

[0029] where k r is the arc coefficient, j = 1, 2, 3 correspond to the three-phase electrodes respectively; the smelting process uses the three-phase drive motor to adjust the electrode position and thus change the arc length, and the three-phase drive motor rotation speed u j (t) has the following relationship with the arc length:

[0030] L j (t)-L j (tT) = k L u j (tL′) (6)

[0031] where k L is the transmission coefficient of the actuator, and L' is the lag time. From equations (4)-(6), we can see that the electrode current y j (t) and motor rotation speed u j (t) There is the following relationship:

[0032] y j (t)-y j (tT)=bu j (tL′)+V(t) (7)

[0033] Where b = k y k r k L , V(t)=k y (V0(t)-V0(tT)); From the above formula, we can know that near the working point of the fused magnesium furnace, the three-phase electrode current yj (t) and the three-phase traction motor rotation speed u j The model of (t) consists of a linear model with pure lag L' and a bounded unmodeled dynamic V(T); for the model shown in the above formula, a preset time algorithm is used to adjust the rotation speed u of the three-phase drive motor under the condition of charging and melting. j (t) makes the three-phase electrode current y j (t) Tracking three-phase electrode current setting value

[0034] The output signal u of the PID controller is:

[0035]

[0036] where k p1 is the proportionality coefficient, k I1 is the integration coefficient, k d1 is the differential coefficient, e(t) is the three-phase electrode current tracking error;

[0037] A finite time system control method for fused magnesium furnace based on time-varying feedback is adopted, which is called "preset time control". The key to the preset time control design is to introduce a time-varying scaling function:

[0038]

[0039] Where T is a time function, T≥t1>0, and μ1(0)=1, μ1(T)=+∞.

[0040] According to the above steps, the tracking error of the three-phase electrode current is determined as:

[0041]

[0042] According to the tracking error e(t), the preset time consistency control is proposed, and the control input u(t) of the electric magnesium furnace equipment, that is, the rotation speed of the three-phase drive motor, is obtained as follows:

[0043]

[0044] Where k>0 is the design parameter; the tracking control of the three-phase electrode current is achieved by selecting the design parameter

[0045] According to the electric fused magnesium furnace three-phase electrode current preset time intelligent loop control method of the present invention, in step four, the following steps are included:

[0046] After designing the controller, the VScode software is used to carry out simulation experiments and verify the effectiveness of the proposed current tracking control method; the three-phase electrode current obtained after the preset time algorithm control is compared with the historical three-phase electrode current, and the corresponding error is calculated to evaluate the performance. At the same time, it is compared with the PID algorithm control, and the actual output and expected output of the three-phase electrode current and the rated change trend of the control input three-phase traction motor speed are plotted.

[0047] The present invention provides a preset time intelligent control method based on major energy-consuming equipment. Compared with the existing technology, the present invention has the following beneficial effects:

[0048] 1. The operation model of the smelting process of the electric magnesium furnace has comprehensive and complex characteristics such as strong nonlinearity, multi-variable coupling, time-varying model parameters, and difficulty in establishing a mathematical model. The introduction of intelligent control methods enables the loop control system to still have good dynamic performance under the conditions of set value changes, frequent interference and changes in operating conditions, thereby improving the intelligence level of the control system during the operation of major energy-consuming equipment.

[0049] 2. Different from the conventional finite time control (the finite stabilization time is not uniform under the initial conditions) and the fixed time control (the stabilization time cannot be given arbitrarily), the preset time control proposed by the present invention enables the convergence time to be given in advance within the physically allowed range, thereby realizing rapid current tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is the structural diagram of the electric magnesium furnace system with end-edge-cloud collaboration.

[0051] Figure 2 The effect diagram of the molten magnesium furnace under the traditional PID control method. (a) is the current signal; (b) is the control signal; (c) is the gain change.

[0052] Figure 3 The effect diagram of the molten magnesium furnace under the preset time PID control method. (a) is the current signal; (b) is the control signal; (c) is the gain change. DETAILED DESCRIPTION

[0053] The following is a further detailed description of the preset time intelligent control method based on major energy-consuming equipment of the present invention in conjunction with the accompanying drawings and embodiments.

[0054] Based on the preset time intelligent control method of major energy-consuming equipment, the smelting process of major energy-consuming equipment represented by the electric magnesium furnace has comprehensive complexity such as strong coupling of multiple variables, strong nonlinearity, unknown parameters, and dynamic performance changes with operating conditions. Therefore, a well-designed high-performance controller that tracks the optimal melting current setting value has become a key factor in reducing energy consumption per ton. The controlled object of the electric magnesium furnace loop process uses the three-phase electrode current as output and the three-phase traction motor speed and direction as input. The preset time control method is used so that the output of the controlled object can quickly track the changing current value to ensure the safe and stable operation of the production process. Specifically, it includes the following steps:

[0055] (1) The electric fused magnesium furnace was selected as the research object and the equipment characteristics were analyzed. The production index of the smelting process of major energy-consuming equipment represented by the electric fused magnesium furnace is the electric energy consumed per ton of qualified products, that is, the unit energy consumption;

[0056] (2) The controlled objects of the electric fused magnesium furnace control system include the unit energy consumption of the electric fused magnesium furnace and the three-phase electrode current of the electric fused magnesium furnace. The controlled quantity is the rotation speed and direction of the three-phase traction motor of the electric fused magnesium furnace. The unit energy consumption of the product in the smelting process is directly affected by the size and stability of the three-phase electrode current value;

[0057] (3) Analyze the relationship between the three-phase electrode current of the electric magnesium furnace and the rotation speed of the three-phase drive motor. According to the deviation between the actual three-phase electrode current value and the set value of the three-phase electrode current under heating and melting conditions, a preset time consistency control algorithm based on self-regulating gain is used to obtain the speed and direction of the three-phase drive motor under heating and melting conditions.

[0058] (4) Adjust the parameters of the preset time consistency control scheme in step 3, verify the preset time algorithm and compare it with the traditional control method PID algorithm.

[0059] The electric fused magnesium furnace was selected as the research object and the equipment characteristics were analyzed. The production indicator of the smelting process of major energy-consuming equipment represented by the electric fused magnesium furnace is the electric energy consumed per ton of qualified products, that is, the unit energy consumption.

[0060] The unit energy consumption index used to reflect the energy efficiency of the product during the smelting process of the electric fused magnesium furnace is calculated by the following formula:

[0061]

[0062] Among them, r represents the unit energy consumption of the electric fused magnesium furnace, E represents the total electric energy consumed in a complete smelting process of the electric fused magnesium furnace, and m represents the total output of qualified products obtained after a complete smelting process of the electric fused magnesium furnace. In order to reduce energy consumption, the control target of the smelting process of the electric fused magnesium furnace is to control the unit energy consumption of the product within the target value range and as small as possible under the condition of meeting the production constraint in advance. That is,

[0063] Min(r)

[0064]

[0065] in Indicates the lower limit of the output of the fused magnesium furnace. and They represent the upper and lower limits of the unit energy consumption of the fused magnesium furnace respectively. The target value of unit energy consumption of electric fused magnesium furnace is r * The allowable fluctuation range.

[0066] The controlled objects of the electric fused magnesium furnace control system include the unit energy consumption and three-phase electrode current of the electric fused magnesium furnace. The controlled quantity is the rotation speed and direction of the three-phase traction motor. The unit energy consumption of the product in the smelting process is directly affected by the size and stability of the three-phase electrode current value.

[0067] The controlled objects of the electric magnesium furnace control system include the unit energy consumption r of the product and the three-phase electrode current y j (t), j = 1, 2, 3, the control quantity is the rotation speed and direction ±u of the three-phase traction motor j (t); where r and y j The expressions of (t) are:

[0068] r=f1(y j (t),S L ,B1,B2,B3,B4,B5,m)

[0069] y j (t) = f2(B1, B2, B3, B4, B5, h n ,ρ m.A ,ρ m.B ,h m ,ρ n ,r0,l)

[0070]

[0071] Δy j (t)≤Δy max

[0072] u min <|u j (t)|≤u max

[0073] Where f1(·) is an unknown nonlinear function describing the relationship between the unit energy consumption r of the fused magnesium furnace and its influencing factors, r and the three-phase electrode current value y j (t), current smelting condition S L, melting voltage B1, electrode diameter B2, furnace diameter B3, raw material particle length B4, raw material impurity composition B5 and product output m parameters; f2(·) is the parameter describing the three-phase electrode current y j (t) is an unknown nonlinear function of the relationship between it and its influencing factors, y j (t) and boundary conditions B1, .., B5, layer thickness h n 、Arc resistivity ρ m.A 、Resistivity of molten pool ρ m.B , molten pool depth h m , material layer resistivity ρ n , the spherical radius r0 of the electrode end and the electrode spacing l; I min and I max Respectively represent the three-phase electrode current setting values The upper and lower limits of i=1, ···, 3 represent the three-phase electrode current setting values ​​under the three working conditions of heating and melting, feeding and exhausting respectively; Δy j (t) represents the rate of change of the three-phase electrode current, Δy max Indicates the upper limit of the current change rate; u min and u max Respectively represent the control quantity u j (t) upper and lower limits; during the smelting process, when the three-phase electrode current can stably track the appropriate current setting value, the furnace temperature is guaranteed to be maintained within the range of 2750℃-2850℃, thereby controlling the energy consumption per ton within a certain indicator.

[0074] The relationship between the three-phase electrode current of the electric magnesium furnace and the rotation speed of the three-phase traction motor is analyzed. According to the deviation between the actual three-phase electrode current value and the set value of the three-phase electrode current under heating and melting conditions, a preset time consistency control algorithm based on self-adjusting gain is used to obtain the speed and direction of the three-phase traction motor under heating and melting conditions.

[0075] During the smelting process, the electrode voltage is fixed, and the dynamic characteristics of the three-phase electrode current and the corresponding arc resistance near the working point of the electric magnesium furnace show linear characteristics:

[0076]

[0077] where k y is the current coefficient, V0(t) is the bounded unmodeled dynamic term; arc resistance With arc length L j is proportional to each other, that is:

[0078]

[0079] where k ris the arc coefficient, j = 1, 2, 3 correspond to the three-phase electrodes respectively; the smelting process uses the three-phase drive motor to adjust the electrode position and thus change the arc length, and the three-phase drive motor rotation speed u j (t) has the following relationship with the arc length:

[0080] L j (t)-L j (tT) = k L u j (tL′)

[0081] where k L is the transmission coefficient of the actuator, L' is the lag time; the three-phase electrode current y j (t) and the three-phase traction motor rotation speed u j (t) There is the following relationship:

[0082] y j (t)-y j (tT)=bu j (tL′)+V(t)

[0083] Where b = k y k r k L , V(t)=k y (V0(t)-V0(tT)); From the above formula, we can know that near the working point of the fused magnesium furnace, the three-phase electrode current y j (t) and the three-phase traction motor rotation speed u j The model of (t) consists of a linear model with pure lag L' and a bounded unmodeled dynamic V(T); for the model shown in the above formula, a preset time algorithm is used to adjust the rotation speed u of the three-phase drive motor under the condition of charging and melting. j (t) makes the three-phase electrode current y j (t) Tracking three-phase electrode current setting value

[0084] The output signal u of the PID controller is:

[0085]

[0086] where k p1 is the proportionality coefficient, k I1 is the integration coefficient, k d1 is the differential coefficient, e(t) is the three-phase electrode current tracking error;

[0087] A finite time system control method for fused magnesium furnace based on time-varying feedback is adopted, which is called "preset time control". The key to the preset time control design is to introduce a time-varying scaling function:

[0088]

[0089] Where T is a time function, T≥t1>0, and μ1(0)=1, μ1(T)=+∞;

[0090] According to the above steps, the tracking error of the three-phase electrode current is determined as:

[0091]

[0092] According to the tracking error e(t), the preset time consistency control is proposed, and the control input u(t) of the electric magnesium furnace equipment, that is, the rotation speed of the three-phase drive motor, is obtained as follows:

[0093]

[0094] Wherein k>0 is a design parameter; the tracking control of the three-phase electrode current is realized by selecting the design parameter.

[0095] The parameters of the preset time consistency control scheme in step three are adjusted, the preset time algorithm is verified and compared with the traditional control method PID algorithm.

[0096] After designing the controller, the VScode software is used to carry out simulation experiments and verify the effectiveness of the proposed current tracking control method; the three-phase electrode current obtained after the preset time algorithm control is compared with the historical three-phase electrode current, and the corresponding error is calculated to evaluate the performance. At the same time, it is compared with the PID algorithm control, and the actual output and expected output of the three-phase electrode current and the rated change trend of the control input three-phase traction motor speed are plotted.

[0097] Intelligent system of fused magnesium furnace Figure 1 As shown in the figure, it consists of the end-actual operation control system, the edge-preset time controller system and the cloud-preset time control process digital twin system. The control system consists of a preset time control system and a data acquisition and transmission device. The preset time control system consists of a PLC control system that executes the preset time control algorithm and a controlled object, realizing the closed-loop control of the preset time controller on the controlled object, so that the output of the controlled object tracks the set value.

[0098] The smelting process of the electric magnesium furnace has always been carried out manually. The current value fluctuates greatly during manual control, and the current tracking error often exceeds the allowable range of the tracking error. In order to verify the effectiveness of the preset time control method for tracking current proposed in the present invention, the tracking current setting value is switched to the PID control algorithm and the preset time control algorithm respectively and applied to the smelting process. In this process, the current setting value is manually given as The specified allowable range of current tracking error is [-2000A, 2000A], and the output signal range of the controller is [-40Hz, 40Hz]. The control target of the electric magnesium furnace production process is as shown in formula (12), and the five indicators of mean square error (MSE), mean absolute error (MAE), frequency of system reaching target value (IHR), cumulative effect of system error (IAEI), and smoothness of system input (CIM) are used to evaluate the control method.

[0099]

[0100] First, the PID control system is used to realize the closed-loop control of the PID controller on the controlled object, so that the output of the controlled object tracks the set value. After debugging, the parameters of the three PID controllers of the three-phase electrode current are determined to be k p1 =0.7, k I1 =0.003, k d1 =0.038. Next, the preset time control algorithm is used to track the electrode current, and after debugging, the parameter k is determined to be 0.36.

[0101] The control effects of the PID control method and the preset time PID control method are as follows: Figure 2 and Figure 3 The evaluation results are shown in Table 1. Figure 2 , Figure 3 It can be seen from Table 1 that by adopting the preset time control method based on self-adjusting gain, the number of current root total error exceeding the allowable error range is significantly reduced, which effectively improves the tracking error convergence accuracy and convergence speed of the loop control and ensures the transient and steady-state performance of the tracking error.

[0102] Table 1

[0103]

[0104] The above numerical simulation results prove the correctness and effectiveness of the preset time intelligent control method based on major energy-consuming equipment. It has been successfully applied in the control of electric magnesium furnace and achieved significant energy-saving and emission reduction effects.

Claims

1. A method for controlling the preset time of three-phase electrode current in an electric fused magnesium furnace by an intelligent circuit, characterized in that: The controlled object of the fused magnesium furnace loop process takes the three-phase electrode current as output and the three-phase traction motor speed and direction as input. The preset time control method is adopted to enable the output of the controlled object to quickly track the changing current value to ensure the safe and stable operation of the production process; specifically, the following steps are included: Step 1: Select the fused magnesium furnace as the research object and analyze the equipment characteristics. The production index of the smelting process of major energy-consuming equipment represented by the fused magnesium furnace is the electric energy consumed per ton of qualified products, that is, the unit energy consumption; Step 2: The controlled objects of the fused magnesium furnace control system include the unit energy consumption of the fused magnesium furnace and the three-phase electrode current of the fused magnesium furnace. The controlled quantity is the rotation speed and direction of the three-phase traction motor of the fused magnesium furnace. The unit energy consumption of the fused magnesium furnace during the smelting process is directly affected by the size and stability of the three-phase electrode current value. Step three, analyzing the relationship between the three-phase electrode current of the electric magnesium furnace and the rotation speed of the three-phase drive motor, according to the deviation between the actual three-phase electrode current value and the three-phase electrode current set value under the heating and melting conditions, using a preset time consistency control algorithm based on self-regulating gain to obtain the speed and direction of the three-phase drive motor under the heating and melting conditions; Step 4: Adjust the parameters of the preset time consistency control scheme in step 3, verify the preset time algorithm and compare it with the traditional control method PID algorithm.

2. The method for controlling the three-phase electrode current preset time of a fused magnesium furnace according to claim 1 is characterized in that: The electric fused magnesium furnace was selected as the research object and the equipment characteristics were analyzed. The production index of the smelting process of the major energy-consuming equipment represented by the electric fused magnesium furnace is the electric energy consumed per ton of qualified products, that is, the unit energy consumption; The unit energy consumption index used to reflect the energy efficiency of the product during the smelting process of the electric fused magnesium furnace is calculated by the following formula: Where r represents the unit energy consumption of the fused magnesium furnace, E represents the total electric energy consumed in a complete smelting process of the fused magnesium furnace, and m represents the total output of qualified products obtained after a complete smelting process of the fused magnesium furnace. In order to reduce energy consumption, the control target of the smelting process of the fused magnesium furnace is to control the unit energy consumption of the product within the target value range and as small as possible while meeting the production constraint in advance; that is, Min(r) in Indicates the lower limit of the output of the fused magnesium furnace. and They represent the upper and lower limits of the unit energy consumption of the fused magnesium furnace respectively. The target value of unit energy consumption of electric fused magnesium furnace is r * The permissible fluctuation range.

3. The method for controlling the three-phase electrode current preset time of a fused magnesium furnace according to claim 1, characterized in that: The controlled objects of the fused magnesium furnace control system include the unit energy consumption of the fused magnesium furnace and the three-phase electrode current of the fused magnesium furnace. The controlled quantity is the rotation speed and direction of the three-phase traction motor of the fused magnesium furnace. The unit energy consumption of the fused magnesium furnace during the smelting process is directly affected by the size and stability of the three-phase electrode current value. The controlled objects of the electric fused magnesium furnace control system include the unit energy consumption r of the electric fused magnesium furnace and the three-phase electrode current y j (t), j = 1, 2, 3, the control quantity is the rotation speed and direction ±u of the three-phase traction motor j (t); where r and y j The expressions of (t) are: r=f1(y j (t),S L ,B1,B2,B3,B4,B5,m) y j (t)=f2(B1,B2,B3,B4,B5,h n ,ρ m.A ,ρ m.B ,h m ,ρ n ,r0,l) Δy j (t)≤Δy max u min <|u j (t)|≤u max Where f1(·) is an unknown nonlinear function describing the relationship between the unit energy consumption r of the fused magnesium furnace and its influencing factors, r and the three-phase electrode current value y j (t), current smelting condition S L , melting voltage B1, electrode diameter B2, furnace diameter B3, raw material particle length B4, raw material impurity composition B5 and product output m parameters; f2(·) is the parameter describing the three-phase electrode current y j (t) is an unknown nonlinear function of the relationship between it and its influencing factors, y j (t) and boundary conditions B1, .., B5, layer thickness h n 、Arc resistivity ρ m.A , molten pool resistivity ρ m.B , molten pool depth h m , material layer resistivity ρ n , the spherical radius r0 of the electrode end and the electrode spacing l; I min and I max Respectively represent the three-phase electrode current setting values The upper and lower limits of i=1, ···, 3 represent the three-phase electrode current setting values ​​under the three working conditions of heating and melting, feeding and exhausting respectively; Δy j (t) represents the rate of change of the three-phase electrode current, Δy max Indicates the upper limit of the current change rate; u min and u max They represent the control quantity u of the fused magnesium furnace respectively. j (t) upper and lower limits; during the smelting process, when the three-phase electrode current can stably track the appropriate current setting value, the furnace temperature is guaranteed to be maintained within the range of 2750℃-2850℃, thereby controlling the energy consumption per ton within a certain indicator.

4. The method for controlling the three-phase electrode current preset time of a fused magnesium furnace according to claim 1, characterized in that: The relationship between the three-phase electrode current of the electric magnesium furnace and the rotation speed of the three-phase drive motor is analyzed. According to the deviation between the actual three-phase electrode current value and the set value of the three-phase electrode current under heating and melting conditions, the preset time consistency control algorithm based on self-regulating gain is used to obtain the speed and direction of the three-phase drive motor under heating and melting conditions. During the smelting process, the electrode voltage is fixed, and the dynamic characteristics of the three-phase electrode current and the corresponding arc resistance near the working point of the electric magnesium furnace show linear characteristics: where k y is the current coefficient, V0(t) is the bounded unmodeled dynamic term; Arc resistance With arc length L j is proportional to each other, that is: where k r is the arc coefficient, j = 1, 2, 3 correspond to the three-phase electrode respectively; the smelting process uses the three-phase drive motor to adjust the electrode position and thus change the arc length, and the three-phase drive motor rotation speed u j (t) has the following relationship with the arc length: L j (t)-L j (t-T)=k L u j (t-L′) where k L is the transmission coefficient of the actuator, L′ is the lag time; the three-phase electrode current y j (t) and the rotation speed u of the three-phase traction motor j (t) There is the following relationship: y j (t)-y j (tT)=bu j (tL′)+V(t) Where b = k y k r k L , V(t)=k y (V0(t)-V0(tT)); From the above formula, we can know that near the working point of the fused magnesium furnace, the three-phase electrode current y j (t) and the three-phase traction motor rotation speed u j The model of (t) consists of a linear model with pure lag L′ and a bounded unmodeled dynamic V(T); for the model shown in the above formula, a preset time algorithm is used to adjust the rotation speed u of the three-phase drive motor under the condition of charging and melting. j (t) makes the three-phase electrode current y j (t) Tracking three-phase electrode current setting value The output signal u of the PID controller is: where k p1 is the proportionality coefficient, k I1 is the integration coefficient, k d1 is the differential coefficient, e(t) is the three-phase electrode current tracking error; A finite time system control method for fused magnesium furnace based on time-varying feedback is adopted, which is called "preset time control". The key to the preset time control design is to introduce a time-varying scaling function: Where T is a time function, T≥t1>0, and μ1(0)=1, μ1(T)=+∞; According to the above steps, the tracking error of the three-phase electrode current is determined as: According to the tracking error e(t), the preset time consistency control is proposed, and the control input u(t) of the electric magnesium furnace equipment, that is, the rotation speed of the three-phase drive motor, is obtained as follows: Wherein k>0 is a design parameter; the tracking control of the three-phase electrode current is realized by selecting the design parameter.

5. The method for controlling the three-phase electrode current preset time of a fused magnesium furnace according to claim 1, characterized in that: Adjust the parameters of the preset time consistency control scheme in step 3, verify the preset time algorithm and compare it with the traditional control method PID algorithm; After designing the controller, use VScod e The software conducts simulation experiments and verifies the effectiveness of the proposed current tracking control method; compares the three-phase electrode current obtained after the preset time algorithm control with the historical three-phase electrode current, calculates the corresponding error to evaluate the performance, and compares it with the PID algorithm control, and draws the actual output and expected output diagram of the three-phase electrode current and the rated change trend diagram of the control input three-phase traction motor speed.

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