Method for improving power supply continuity of electric arc furnace

Abstract

The invention relates to a method for improving power supply continuity of an electric arc furnace. The method comprises the following steps that a power source is started, the electric arc furnace carries out steelmaking, the maximum value of generated three-phase current values is sampled, and data obtained through sampling forms a data queue; analyzing the data of the data queue, determining abnormal data, and calculating the proportion of the abnormal data in the data queue; the abnormal data proportion is compared with an unsteady state critical value, if the abnormal data proportion is equal to or larger than the unsteady state critical value, it is judged that the electric arc furnace steelmaking is in an unsteady state operation state at the moment, and the voltage gear is reduced by one gear; meanwhile, the steady-state clock is reset, the data queue is emptied, sampling is conducted again, and after a new data queue is formed, the steady-state clock is started to start timing; and if the proportion of the abnormal data is continuously smaller than the non-steady-state critical value before the steady-state judgment time is reached, it is judged that the electric arc furnace steelmaking is in the steady-state operation state at the moment, the voltage gear is increased by one gear, and meanwhile the steady-state clock is returned to zero. The power supply continuity is improved, and then the overall power supply stability and efficiency in the waste steel melting period are improved.

Description

Technical Field

[0001] The invention relates to a method for improving the power supply continuity of an electric arc furnace, and belongs to the field of electric arc furnace steelmaking. Background Art

[0002] Power supply operation is one of the main operations of electric arc furnace steelmaking. During the smelting process, a continuous arc is a necessary condition for the efficient production of the electric arc furnace. During the melting of scrap steel, the arc length changes frequently due to unstable factors such as the different types and sizes of scrap steel, the arc burying effect of slag and the collapse of scrap steel. It is easy to have over-adjustment, arc breaking and power outage, resulting in low active power and prolonged smelting time. Generally, the higher the voltage level, the higher the rated active power, but the arc continuity is poor; the lower the voltage level, the lower the rated active power, but the arc stability is better. Therefore, choosing the right voltage level is crucial for the efficient production of the electric arc furnace.

[0003] During the smelting process of the electric arc furnace, the continuity of the arc is generally maintained by the electric arc furnace operator and the electrode adjustment system. The operator inputs the voltage level to the electrode adjustment system, and the electrode adjustment system stabilizes the actual current value near the rated current by adjusting the length of the arc. When the working parameters of the electrode adjustment system do not match the scrap steel structure, the actual current value fluctuates greatly and the power supply is discontinuous. If the operator judges that the current power supply continuity is poor and there is a risk of arc breaking or power outage based on the electrical data, the voltage level is adjusted to make the power supply return to a stable state. When the power supply continuity is good, the operator increases the power supply power by adjusting the voltage level to speed up the smelting rhythm. However, in the actual smelting process, due to the rapid change of electrical data and the lack of data reference for manual judgment, it can only rely on experience, which increases the difficulty for operators to make accurate judgments, and often leads to missed judgments or misjudgments.

[0004] Therefore, it is necessary to provide an automatic determination method for power supply continuity during the scrap steel melting stage to solve the problem of manual missed determination or misjudgment. Summary of the invention

[0005] The present invention provides a method for improving the continuity of power supply of an electric arc furnace, solves the problem of manual missed judgment or misjudgment, improves the continuity of power supply, and further improves the overall power supply efficiency during the melting of scrap steel.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for improving the continuity of power supply to an electric arc furnace comprises the following steps:

[0008] Step S1: Start the power supply, the electric arc furnace is used for steelmaking, and the maximum value of the three-phase current value generated is sampled, and the sampled data forms a data queue;

[0009] Step S2: Analyze the data in the data queue in step S1, determine abnormal data, and calculate the proportion of abnormal data in the data queue;

[0010] Step S3: Preset a non-steady-state critical value, compare the abnormal data ratio obtained in step S2 with the non-steady-state critical value, if the abnormal data ratio is equal to or greater than the non-steady-state critical value, proceed to step S4, if the abnormal data ratio is continuously less than the non-steady-state critical value, directly proceed to step S5;

[0011] Step S4: If the abnormal data ratio obtained in step S2 reaches the non-steady-state critical value, it is determined that the electric arc furnace steelmaking is in a non-steady-state operation state at this time, and the voltage gear is reduced by 1 gear; at the same time, the steady-state clock is reset to zero, the data queue is cleared and resampled, and after a new data queue is formed, the steady-state clock is started to start timing, and step S5 is performed;

[0012] Step S5: preset the steady-state determination time of the steady-state clock. If the abnormal data ratio is continuously less than the non-steady-state critical value before the steady-state determination time is reached, it is determined that the electric arc furnace steelmaking is in a steady-state operation state at this time, the voltage level is increased by 1 level, and the steady-state clock is reset to zero at the same time; the electric arc furnace power supply stable operation is completed;

[0013] Furthermore, the three-phase current value is the current value of the secondary side of the transformer;

[0014] Furthermore, a specific method for sampling the maximum value of the three-phase current is to collect data according to a preset period, set N data into a queue, put a new data into the end of the queue each time it is sampled, and remove the data at the head of the queue at this time;

[0015] Furthermore, the preset period is less than or equal to 500 ms;

[0016] Furthermore, the criterion for determining abnormal data in step S2 is:

[0017] Xi>α×Imax

[0018] Where Xi is the i-th current data in the data queue; α is the abnormality determination coefficient, 0<α<1; Imax is the maximum safe current;

[0019] Furthermore, when the voltage level is lowered in step S4, the voltage level is greater than or equal to the minimum voltage level corresponding to the electric arc furnace steelmaking in real time;

[0020] Furthermore, when the voltage level is increased in step S5, the voltage level is less than or equal to the target voltage level corresponding to the electric arc furnace steelmaking in real time.

[0021] Through the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0022] The method for improving the power supply continuity of an electric arc furnace provided by the present invention is based on the current situation of different types and sizes of scrap steel, the arc burying effect of slag and scrap steel collapse pointed out in the background technology, takes the judgment result of power supply continuity as a basis, and reasonably adjusts the voltage gear to reduce the frequency of over-regulation, arc breaking and power outages, thereby improving the continuity of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 1 It is a flow chart of a method for improving the power supply continuity of an arc furnace according to a preferred embodiment of the present invention;

[0025] Figure 2 It is a voltage curve diagram of the preferred embodiment provided by the present invention when it is implemented. DETAILED DESCRIPTION

[0026] The present invention will now be described in further detail with reference to the accompanying drawings.

[0027] When electric arc furnace steelmaking operations are carried out in steel mills, power supply stability problems are generally judged manually, and the voltage level is adjusted manually. This often leads to missed or misjudgment. Based on actual working conditions, if a power outage occurs, the time interval for the high-voltage power supply line to trip can reach 1 minute. If over-adjustment or arc failure occurs, the power supply will be reduced, which will have a significant impact on production efficiency.

[0028] Therefore, the present application provides a method for improving the continuity of power supply of an electric arc furnace, which uses the data involved in the smelting of the electric arc furnace itself as the basis for adjusting the voltage level and giving an early warning of current fluctuations. At the same time, the provided method can also use these data as a reference for judging whether the power supply is continuous, as shown in the following example. Figure 1 As shown, the following steps are included:

[0029] Step S1: Start the power supply, the electric arc furnace is used for steelmaking, and the maximum value of the three-phase current value generated is sampled. The sampled data forms a data queue; the three-phase current value here is the secondary side current value of the transformer. This is because the working characteristics of the electric arc furnace determine that its demand for current will change with different working stages, and the secondary side current value of the transformer can directly reflect the changes in the current demand of the electric arc furnace in each working stage, thereby making the judgment of abnormal data more accurate.

[0030] The specific method for sampling the maximum value of the three-phase current is to collect data according to a preset period, set N data into a queue, put a new data into the end of the queue each time it is sampled, and remove the data at the head of the queue at this time.

[0031] This collection method can cope with the volatility of current under the constantly changing working conditions of the arc furnace, and quickly adapt to such changes. For example, queuing the data is helpful for analyzing the changing trend of the current. By observing the data changes over a period of time, the long-term trend and periodic changes of the current can be found, providing a more comprehensive basis for judging the continuity of the arc furnace. Only a fixed amount of data is retained each time, which can meet the analysis needs without taking up too many storage resources. By discarding the old data at the head of the queue, the data queue always keeps an eye on the current status, and changes in the proportion of abnormal data can be detected more quickly. All of the above means can ensure that the arc furnace takes corresponding adjustment measures in a timely manner (including lowering or increasing the voltage gear), achieves continuous and adaptive monitoring, and improves the adaptability and accuracy of stability judgment.

[0032] Of course, continuous monitoring of current data requires presetting a collection period for all data collection in advance. Preferably, in the present application, the preset period is less than or equal to 500ms.

[0033] Step S2: Analyze the data in the data queue in step S1, determine abnormal data, and calculate the proportion of abnormal data in the data queue;

[0034] The determination criteria for abnormal data are usually related to the set abnormal determination coefficient and the preset safety current. Therefore, preferably, the determination criteria provided by the present application are:

[0035] Xi>α×Imax

[0036] Wherein, Xi is the i-th current data in the data queue; α is the abnormality determination coefficient, 0<α<1; Imax is the maximum safe current.

[0037] Step S3: Preset a non-steady-state critical value, compare the abnormal data ratio obtained in step S2 with the non-steady-state critical value, if the abnormal data ratio is equal to or greater than the non-steady-state critical value, proceed to step S4, if the abnormal data ratio is continuously less than the non-steady-state critical value, proceed directly to step S5.

[0038] The setting of the non-steady-state critical value is actually an empirical value setting parameter, which is obtained through analysis after a large amount of data integration to determine whether the current power supply state is continuous.

[0039] Step S4: If the abnormal data ratio obtained in step S2 reaches the non-steady-state critical value, it is determined that the electric arc furnace steelmaking is in a non-steady-state operation state at this time, and the voltage gear is reduced by 1 gear; at the same time, the steady-state clock is reset to zero, the data queue is cleared and resampled, and after a new data queue is formed, the steady-state clock is started to start timing, and step S5 is performed. It is required to limit in this step that when the voltage gear is reduced, the voltage gear is greater than or equal to the minimum voltage gear corresponding to the real-time electric arc furnace steelmaking.

[0040] Step S5: preset the steady-state judgment time of the steady-state clock. If the proportion of abnormal data is continuously less than the non-steady-state critical value before reaching the steady-state judgment time, it is determined that the electric arc furnace steelmaking is in a steady-state operation state at this time, and the voltage gear is increased by 1 gear, and the steady-state clock is reset to zero at the same time; the electric arc furnace power supply stable operation is completed. It is required to be limited in this step that when the voltage gear is increased, the voltage gear is less than or equal to the target voltage gear corresponding to the real-time electric arc furnace steelmaking.

[0041] The determination of step S4 and step S5 requires continuous sampling and calculation of the abnormal data ratio. This repetitive cyclic operation can monitor the operating status of the arc furnace in real time (to ensure the continuity of power supply) and adjust the voltage level in time to adapt to different working conditions, which has strong adaptability. Continuous sampling and updating of the queue can ensure that the data obtained by the system is more accurate. At this time, dynamically adjusting the voltage level according to the operating status of the arc furnace can effectively reduce power supply fluctuations, improve power supply continuity, and extend the service life of the equipment.

[0042] Obviously, the method provided above, based on the targeted collected data and combined with corresponding method steps, can not only provide a basis for voltage level adjustment, but also determine whether the power supply is continuous during the smelting process.

[0043] In order to verify the feasibility and advantages of the above method, the present application provides specific embodiments, which are described as follows.

[0044] Example:

[0045] An electric arc furnace uses a transformer with a rated power of 45MW for smelting. There are 10 voltage levels, of which 1-6 are constant current levels and 7-10 are constant power levels. The power supply parameters of each level are shown in Table 1.

[0046] Table 1

[0047]

[0048] The smelting process is divided into three stages: arc starting, melting and melting. In the arc starting stage, the minimum voltage level is set to level 4 and the target voltage level is set to level 4; in the melting stage, the minimum voltage level is set to level 8 and the target voltage level is set to level 10; in the melting stage, the minimum voltage level is set to level 6 and the target voltage level is set to level 8. The automatic adjustment process of the power supply level is as follows:

[0049] Step S1: Switch the voltage gear to the target voltage gear 4 of the arc starting stage, the arc furnace operator sends a smelting start signal, the vacuum switch is closed, and the power supply starts. The arc furnace PLC compares the secondary current values ​​of the three-phase electrodes with a cycle of 500 milliseconds, extracts the maximum value to form a data queue, and every 20 data form a queue. Each time a new data is collected, it is put at the end of the queue and the data at the head of the original queue is discarded.

[0050] Step S2: Analyze the data in the data queue in step S1, determine abnormal data, and calculate the proportion of abnormal data in the data queue.

[0051] Step S3: Set the non-steady-state critical value to 0.4, and compare the abnormal data ratio obtained in step S2 with the non-steady-state critical value.

[0052] Next, Figure 2 The six points A, B, C, D, E and F are used as examples to cover various working conditions where the abnormal data ratio is compared with the non-steady-state critical value. In the figure, the horizontal axis represents time in min, the vertical axis on the left side of the diagram represents the voltage level in gear, and the vertical axis on the right side represents the abnormal data ratio.

[0053] like Figure 2 At point A in the figure, the abnormal data ratio reaches 0.4, triggering the non-steady-state condition, and the voltage level is reduced by 1 level, from level 10 to level 9. At the same time, the steady-state clock is reset to zero, the data in the data queue is cleared and the data is collected again. The collection cycle is 500 milliseconds, which takes a total of 10 seconds. During the re-collection of data, the abnormal data ratio is displayed as 0. After the data collection is completed, the abnormal data ratio is calculated normally, and the steady-state clock starts timing.

[0054] like Figure 2 At point B in the figure, the proportion of abnormal data is continuously less than 0.4 during the period from 0 to 30 seconds of the steady-state clock, which meets the steady-state judgment condition. The voltage level is increased by 1 level from 9 to 10.

[0055] like Figure 2 At point C in the figure, the abnormal data ratio reaches 0.4, triggering the non-steady-state judgment condition, and the voltage level is reduced by 1 level, from level 10 to level 9. At the same time, the steady-state clock is reset to zero, the data in the data queue is cleared and the data is collected again. The collection cycle is 500 milliseconds, which takes a total of 10 seconds. During the re-collection of data, the abnormal data ratio is displayed as 0. After the data collection is completed, the abnormal data ratio is calculated normally, and the steady-state clock starts timing.

[0056] like Figure 2At point D in the figure, when the steady-state clock reaches 25 seconds and the steady-state judgment condition is not met, the abnormal data ratio reaches 0.4. The non-steady-state judgment condition is triggered again, and the voltage level is reduced by 1 level, from level 9 to level 8. At the same time, the steady-state clock is reset to zero, the data in the data queue is cleared and the data is collected again. The collection cycle is 500 milliseconds, which takes a total of 10 seconds. The abnormal data ratio during the re-collection of data is displayed as 0. After the data collection is completed, the abnormal data ratio is calculated normally, and the steady-state clock starts timing.

[0057] like Figure 2 At point E in the figure, the proportion of abnormal data is continuously less than 0.4 during the period from 0 to 30 seconds of the steady-state clock, which meets the steady-state judgment condition. The voltage level is increased by 1 level, from 8 to 9, and the steady-state clock is reset to zero and restarted.

[0058] like Figure 2 At point F in the graph, when the steady-state clock reaches 30 seconds again and the proportion of abnormal data continues to be less than 0.4, the steady-state judgment condition is met, and the voltage level is increased by 1 level from level 9 to level 10.

[0059] In summary, the method for improving the continuity of power supply to an arc furnace provided in this application provides a method for determining the continuity of the power supply state of an arc furnace, and automatically adjusts the voltage level according to the determination result, effectively reducing the probability of overshoot, arc breaking and power tripping during the melting of scrap steel, and improving the power supply efficiency of the arc furnace. At the same time, the algorithm of this application is simple, and no hardware equipment needs to be added. It can be implemented by programming in a PLC or a primary control system of an arc furnace.

[0060] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0061] The meaning of "and / or" described in this application means that the situations where each exists alone or both exist at the same time are included.

[0062] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0063] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for improving the continuity of power supply to an electric arc furnace, characterized in that: The following steps are involved: Step S1: Start the power supply, the electric arc furnace is used for steelmaking, and the maximum value of the three-phase current value generated is sampled, and the sampled data forms a data queue; Step S2: Analyze the data in the data queue in step S1, determine abnormal data, and calculate the proportion of abnormal data in the data queue; Step S3: Preset a non-steady-state critical value, compare the abnormal data ratio obtained in step S2 with the non-steady-state critical value, if the abnormal data ratio is equal to or greater than the non-steady-state critical value, proceed to step S4, if the abnormal data ratio is continuously less than the non-steady-state critical value, directly proceed to step S5; Step S4: If the abnormal data ratio obtained in step S2 reaches the non-steady-state critical value, it is determined that the electric arc furnace steelmaking is in a non-steady-state operation state at this time, and the voltage gear is reduced by 1 gear; at the same time, the steady-state clock is reset to zero, the data queue is cleared and resampled, and after a new data queue is formed, the steady-state clock is started to start timing, and step S5 is performed; Step S5: preset the steady-state judgment time of the steady-state clock. If the proportion of abnormal data is continuously less than the non-steady-state critical value before the steady-state judgment time is reached, it is determined that the electric arc furnace steelmaking is in a steady-state operation state at this time, the voltage level is increased by 1 level, and the steady-state clock is reset to zero at the same time; thus completing the stable power supply operation of the arc furnace.

2. The method for improving the power supply continuity of an electric arc furnace according to claim 1, characterized in that: The three-phase current value is the current value of the secondary side of the transformer.

3. The method for improving the power supply continuity of an electric arc furnace according to claim 1, characterized in that: The specific method for sampling the maximum value of the three-phase current is to collect data according to a preset period, set N data into a queue, put a new data into the end of the queue each time it is sampled, and remove the data at the head of the queue at this time.

4. The method for improving the continuity of power supply to an electric arc furnace according to claim 3, characterized in that: The preset period is less than or equal to 500 ms.

5. The method for improving the power supply continuity of an arc furnace according to claim 1, characterized in that: The criteria for determining abnormal data in step S2 are: Xi>α×Imax Wherein, Xi is the i-th current data in the data queue; α is the abnormality determination coefficient, 0<α<1; Imax is the maximum safe current.

6. The method for improving the continuity of power supply to an electric arc furnace according to claim 1, characterized in that: When the voltage level is lowered in step S4, the voltage level is greater than or equal to the minimum voltage level corresponding to the electric arc furnace steelmaking in real time.

7. The method for improving the continuity of power supply to an electric arc furnace according to claim 1, characterized in that: When the voltage level is increased in step S5, the voltage level is less than or equal to the target voltage level corresponding to the electric arc furnace steelmaking in real time.

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