High-efficiency arc stabilizing device and method for direct current arc furnace

Abstract

The present application relates to a kind of high-efficiency arc stabilizing device and method of direct current arc furnace, belong to arc furnace field.The present application receives the deviation of load current given value and actual value by current comparator, to obtain load current deviation value;Through fuzzy bandwidth controller, the change rate of load current deviation and load current deviation are combined, after fuzzy control, the bandwidth value required by hysteresis regulator is output;According to the comparison result of comparator, and the bandwidth value output by fuzzy bandwidth controller is compared by hysteresis regulator, to obtain the PWM pulse signal required by driving IGBT.The present application has the ability of inhibiting load circuit short circuit and arc breaking simultaneously, and is fast, flexible and high.

Description

Technical Field

[0001] This invention belongs to the field of electric arc furnaces and relates to a high-efficiency arc stabilization device and method for DC electric arc furnaces. Background Technology

[0002] A DC electric arc furnace is a device that uses a high-temperature electric arc generated between positive and negative electrodes to melt ores and metals. The arc load is a multivariable, nonlinear, and strongly coupled time-varying system, subject to severe random interference. Especially when smelting large pieces of scrap steel without foamy slag, the arc is prone to short circuits or arc interruptions, leading to increased power consumption per ton of steel, decreased efficiency, and even affecting the quality of ingots and causing economic losses in the smelting of special steels.

[0003] Traditionally, addressing arc stability issues has primarily involved employing electrode adjustment systems or external arc stabilization devices. Electrode adjustment systems stabilize the arc by adjusting the raising and lowering of electrodes, but this approach suffers from slow adjustment speeds and the risk of damage due to frequent mechanical movements. Therefore, a large reactor is often required in series in the circuit to ensure arc stability. Adding external arc stabilization devices not only increases investment but also requires more floor space, making it generally impractical for retrofit projects. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high-efficiency arc stabilization control device and method for DC electric arc furnace with fast response speed and high flexibility, so as to solve the problems of slow arc stabilization effect and easy damage to mechanical structure of existing DC electric arc furnace.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A high-efficiency arc stabilization device for a DC electric arc furnace includes a current comparator, a fuzzy bandwidth controller, and a current hysteresis regulator.

[0007] The current comparator is used to receive the deviation between the given load current value and the actual value, thereby obtaining the load current deviation value;

[0008] The fuzzy bandwidth controller combines the load current deviation and the rate of change of the load current deviation, and outputs the bandwidth value required by the hysteresis regulator after fuzzy control.

[0009] The current hysteresis regulator performs a hysteresis comparison between the comparison result of the comparator and the output bandwidth value of the fuzzy bandwidth controller, thereby obtaining the PWM pulse signal required to drive the IGBT.

[0010] Preferably, the fuzzy bandwidth controller includes a positive bandwidth h+ fuzzy controller and a negative bandwidth h- fuzzy controller, which operate independently. The positive bandwidth h+ fuzzy controller is used to detect the positive deviation of the load current and the rate of change of the load current deviation, and is used to quickly suppress short-circuit overcurrent. The negative bandwidth h- fuzzy controller is used to detect the negative deviation of the load current and the rate of change of the load current deviation, and is used to quickly suppress current arcing.

[0011] Preferably, the current comparator and current hysteresis regulator can be replaced with a power comparator and a power hysteresis regulator to control the drive pulse according to the given output power.

[0012] Preferably, the efficient arc stabilization method for a DC electric arc furnace suitable for this device includes the following steps:

[0013] S1. The current comparator receives the actual value of the load current and compares it with the given value to obtain the load current deviation value.

[0014] S2. The fuzzy bandwidth controller combines the load current deviation value and the rate of change of the load current deviation value, and after fuzzy control, outputs the bandwidth value h required by the current hysteresis regulator.

[0015] S3. The current hysteresis regulator performs a hysteresis comparison between the comparison result of the current comparator and the bandwidth value output by the fuzzy bandwidth controller to obtain the PWM pulse signal to drive the IGBT.

[0016] S4. Outputs the load voltage required by the electric arc furnace after being chopped by IGBT.

[0017] Furthermore, the bandwidth of the fuzzy bandwidth controller can be calculated using the following formula:

[0018]

[0019] Among them, V a I represents the arc voltage of a DC electric arc furnace. a R represents the voltage drop across the resistance of the circuit conductor, V. dc f represents the DC bus voltage of the electric arc furnace power supply. c The value represents the switching frequency of the IGBT, and L represents the inductance value of the reactor in the electric arc furnace power supply.

[0020] The lower limit of the output bandwidth value of the fuzzy bandwidth controller is:

[0021]

[0022] Among them, f s This indicates the upper limit switching frequency of the IGBT. Exceeding this frequency will cause the IGBT junction temperature to exceed the limit and affect its lifespan.

[0023] The upper limit of the output bandwidth value of the fuzzy bandwidth controller is:

[0024] h max =δ×I n ,

[0025] Where δ is the output current ripple coefficient, I n To output the rated current, the reactor in the power supply is based on h max When designing, if the bandwidth exceeds this value, it will affect the reactor loss and noise, and thus affect the reactor life.

[0026] Furthermore, the output of the fuzzy bandwidth controller includes a positive bandwidth h+ and a negative bandwidth h-, both of which are obtained through fuzzy calculation; the values ​​of both the positive bandwidth h+ and the negative bandwidth h- are within the range of (h... min ,h max ).

[0027] Furthermore, when current is replaced by power, the efficient arc stabilization method for DC electric arc furnaces is also applicable, and the driving pulse is obtained by controlling the given output power.

[0028] The beneficial effects of this invention are as follows: This invention can stabilize the electric arc without frequently adjusting the electrode height without adding an arc stabilization device, and has the ability to simultaneously and quickly suppress load short circuits and arc interruption, improve response speed, reduce switching losses, extend device life, and solve the problems of slow arc stabilization effect and easy damage to mechanical structure in existing DC electric arc furnaces.

[0029] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram of a DC electric arc furnace system;

[0032] Figure 2 Schematic diagram of the arc stabilization control system for the rectifier power supply of a DC electric arc furnace;

[0033] Figure 3 This is a waveform diagram of the output current of the rectifier power supply for a DC electric arc furnace.

[0034] Reference numerals: 101-DC electric arc furnace power supply device; 102-electric arc furnace body; 103-IGBT module; 201-current comparator; 202-fuzzy block controller; 203-current hysteresis regulator. Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] like Figure 1 The diagram shown is a schematic of the DC electric arc furnace system provided in this embodiment, including a DC electric arc furnace power supply device 101 and an electric arc furnace body 102. The DC electric arc furnace power supply device is used to rectify the three-phase AC power and then chop it into the load voltage required by the electric arc furnace through the IGBT module 103 for output.

[0037] like Figure 2 The diagram shows a schematic of the arc stabilization control system for the DC electric arc furnace rectifier power supply in this embodiment. The arc stabilization device includes a current comparator 201, a fuzzy bandwidth controller 202, and a current hysteresis regulator 203.

[0038] The current comparator 201 is used to receive the load current setpoint. Compared with the actual value I a The deviation is used to obtain the load current deviation value ΔI. a The fuzzy bandwidth controller 202 combines the load current deviation ΔI a and the rate of change of load current deviation After fuzzy control, the output current hysteresis regulator 203 obtains the required bandwidth value. In order to handle both short-circuit and arc-breaking conditions, the output bandwidth value includes a positive bandwidth h+ and a negative bandwidth h-. The magnitudes of h+ and h- are independent of each other and are both limited by the bandwidth value range. The current hysteresis regulator 203 performs a hysteresis comparison with the output bandwidth value of the fuzzy bandwidth controller 202 based on the comparison result of the current comparator, thereby obtaining the PWM pulse signal required to drive the IGBT.

[0039] like Figure 3 The figure shown is a waveform of the DC electric arc furnace power supply output current after adjustment based on the arc stabilization device and method of this embodiment. The load current setpoint of this embodiment is... The upper and lower bandwidth constraints derived from the upper switching frequency and output current ripple coefficient of the IGBT are as follows: the upper bandwidth value is h. max =200A, bandwidth lower limit is h min =20A.

[0040] The fuzzy bandwidth controller 202 is based on the load current deviation ΔI a and the rate of change of load current deviation At time t1, the upper limit of the bandwidth is adjusted to h+ = 150A, thereby constraining the upper limit of the load current ripple within this range. This can quickly suppress any subsequent short-circuit faults, protecting the system circuit and power supply unit. At time t2, the fuzzy bandwidth controller 202 adjusts the upper limit of the bandwidth to h- = 100A, thereby constraining the lower limit of the load current ripple within this range. This can quickly suppress any subsequent arc-breaking problems, shorten smelting time, and improve smelting efficiency.

[0041] In summary, the high-efficiency arc stabilization device and method for DC electric arc furnace provided by this invention can stabilize the arc without frequently adjusting the electrode lifting and lowering without adding an arc stabilization device, and has the ability to simultaneously and quickly suppress load short circuits and arc interruption, thereby improving response speed and extending device life.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-efficiency arc-stabilizing device for a DC electric arc furnace, characterized in that: This includes a current comparator, a fuzzy bandwidth controller, and a current hysteresis regulator; The current comparator is used to receive the deviation between the given load current value and the actual value, thereby obtaining the load current deviation value; The fuzzy bandwidth controller combines the load current deviation and the rate of change of the load current deviation, and outputs the bandwidth value required by the current hysteresis regulator after fuzzy control. The current hysteresis regulator performs a hysteresis comparison with the output bandwidth value of the fuzzy bandwidth controller based on the comparison result of the current comparator, thereby obtaining the PWM pulse signal required to drive the IGBT. The fuzzy bandwidth controller includes two independently controlled forward bandwidths. Fuzzy controller and negative bandwidth Fuzzy controller; Forward bandwidth Fuzzy controllers are used to detect positive deviations in load current and the rate of change of load current deviation, and to quickly suppress short-circuit overcurrents. negative bandwidth Fuzzy controllers are used to detect negative deviations in load current and the rate of change of load current deviation, and to quickly suppress current arc interruption.

2. The high-efficiency arc-stabilizing device for a DC electric arc furnace according to claim 1, characterized in that: The current comparator and current hysteresis regulator can be replaced with a power comparator and a power hysteresis regulator.

3. A method for efficient arc stabilization in a DC electric arc furnace applicable to the apparatus described in claim 1 or 2, characterized in that: The method includes the following steps: S1. The current comparator receives the actual value of the load current and compares it with the given value to obtain the load current deviation value. S2. The fuzzy bandwidth controller combines the load current deviation value and the rate of change of the load current deviation value, and outputs the bandwidth value required by the current hysteresis regulator after fuzzy control. S3. The current hysteresis regulator performs a hysteresis comparison between the comparison result of the current comparator and the bandwidth value output by the fuzzy bandwidth controller to obtain the PWM pulse signal to drive the IGBT. S4. Outputs the load voltage required by the electric arc furnace after being chopped by IGBT.

4. The high-efficiency arc-stabilizing device for a DC electric arc furnace according to claim 3, characterized in that: The output of the fuzzy bandwidth controller includes the forward bandwidth. and negative bandwidth Both were obtained through fuzzy calculation; Forward bandwidth and negative bandwidth The range of values ​​is ,in This is the lower limit of the output bandwidth value of the fuzzy bandwidth controller. This represents the upper limit of the output bandwidth value of the fuzzy bandwidth controller.

5. The high-efficiency arc-stabilizing device for a DC electric arc furnace according to claim 4, characterized in that: The upper limit of the output bandwidth value of the fuzzy bandwidth controller is: ， in, The output current ripple factor. To output the rated current; The lower limit of the output bandwidth value of the fuzzy bandwidth controller is: ， in, This indicates the arc voltage of a DC electric arc furnace. This represents the voltage drop across the resistance of the circuit conductor. This indicates the DC bus voltage of the electric arc furnace power supply. This indicates the on-line switching frequency of the IGBT. This indicates the inductance value of the reactor in the electric arc furnace power supply.

6. The high-efficiency arc-stabilizing device for a DC electric arc furnace according to claim 3, characterized in that: The method for efficient arc stabilization of DC electric arc furnaces is also applicable when current is replaced by power.

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