A method and device for current balance control of a submerged arc furnace, a terminal and a storage medium

Abstract

The application provides a method and device for current balance control of a submerged arc furnace, a terminal and a storage medium. The method comprises: obtaining actual three-phase alternating current values of three-phase electrodes of the submerged arc furnace; obtaining a positive sequence transformed total current and an actual negative sequence current value according to the actual three-phase alternating current values; performing PID calculation on the positive sequence transformed total current and a given total current to obtain a first voltage reference value, and performing PID calculation on the actual negative sequence current value and a given negative sequence current to obtain a second voltage reference value; and generating a duty cycle signal for controlling a frequency conversion power supply converter by using the first voltage reference value and the second voltage reference value. The application can realize three-phase current balance output, avoid the negative sequence current problem caused by three-phase current imbalance existing in a traditional transformer type power supply system, improve power quality of the power supply system, and reduce negative effects of the system on a power grid.

Description

Technical Field

[0001] This application relates to the field of control technology for submerged arc furnaces used in metallurgy and chemical industry, and in particular to a current balancing control method, device, terminal and storage medium for submerged arc furnaces. Background Technology

[0002] Three-phase AC submerged arc furnaces used in metallurgy and chemical engineering processes involve the high-temperature reduction of metal and non-metal oxides with carbon. The balanced current output from the three-phase electrodes is essential for providing the necessary thermal energy for smelting production. However, in practical applications, issues such as varying electrode depths into the furnace charge can disrupt the balance of the three-phase current, leading to unbalanced three-phase output power, severe surface arcing, and compromised equipment safety.

[0003] Traditional submerged arc furnaces use transformers as power supply equipment and can only control the three-phase current by collecting phase voltage and current data through sensors to manipulate the electrode raising and lowering. This approach suffers from insufficient reliability, sampling delays, and unsatisfactory automatic control. Manual control relies heavily on experience and technical skill, posing a risk of electrode soft or hard failures, and also easily leading to furnace instability and high energy consumption. These problems increase production costs and reduce the company's economic benefits. Furthermore, to prevent high current from burning out the heating elements, special equipment such as ultra-high capacity circuit breakers and voltage regulating transformers are required, further increasing investment costs. Summary of the Invention

[0004] This application provides a current balancing control method, device, terminal, and storage medium for an electric arc furnace to solve the problem of three-phase current imbalance in the electrodes of an electric arc furnace in the prior art.

[0005] In a first aspect, this application provides a current balancing control method for an electric arc furnace, the method being applied to a variable frequency power supply converter, the variable frequency power supply converter being connected to the three-phase electrodes of the electric arc furnace, the method comprising:

[0006] Obtain the actual value of the three-phase alternating current of the three-phase electrodes of the electric arc furnace;

[0007] The actual values ​​of the positive-sequence transformation total current and the negative-sequence current are obtained based on the actual values ​​of the three-phase AC current.

[0008] A first voltage reference value is obtained by performing PID calculation on the positive sequence transformation total current and the total current setpoint, and a second voltage reference value is obtained by performing PID calculation on the negative sequence current actual value and the negative sequence current setpoint.

[0009] The duty cycle signal for controlling the frequency converter is generated using the first voltage reference value and the second voltage reference value.

[0010] Secondly, this application provides a current balancing control device for an electric arc furnace, comprising:

[0011] The acquisition module is used to acquire the actual value of the three-phase AC current of the three-phase electrodes of the electric arc furnace.

[0012] The first calculation module is used to obtain the actual values ​​of the positive sequence transformation total current and the negative sequence current based on the actual values ​​of the three-phase AC current.

[0013] The second calculation module is used to perform PID calculation on the positive sequence transformation total current and the total current given value to obtain a first voltage reference value, and to perform PID calculation on the negative sequence current actual value and the negative sequence current given value to obtain a second voltage reference value.

[0014] The generation module is used to generate a duty cycle signal for controlling the frequency converter using the first voltage reference value and the second voltage reference value.

[0015] Thirdly, this application provides a terminal including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as described in the first aspect or any possible implementation of the first aspect above.

[0016] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in the first aspect or any possible implementation thereof.

[0017] This application provides a current balancing control method, device, terminal, and storage medium for an electric arc furnace (EAF). The method involves acquiring the actual values ​​of the three-phase AC currents of the three-phase electrodes of the EAF; obtaining the actual values ​​of the positive-sequence total current and the negative-sequence current based on these actual values; performing PID calculations on the positive-sequence total current and the given current value to obtain a first voltage reference value; and performing PID calculations on the actual value of the negative-sequence current and the given current value to obtain a second voltage reference value; and using the first and second voltage reference values ​​to generate a duty cycle signal for controlling a frequency converter. This application uses a frequency converter to achieve balanced three-phase current output, avoiding the negative-sequence current problem caused by three-phase current imbalance in traditional transformer-type power supply systems, improving the power quality of the power supply system, and reducing the negative impact of the system on the power grid. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the implementation of the current balancing control method for an electric arc furnace provided in this application embodiment;

[0020] Figure 2 This is a schematic diagram of the principle of a three-phase frequency conversion AC submerged arc furnace provided in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram of current positive and negative sequence separation provided in an embodiment of this application;

[0022] Figure 4 This is a control diagram illustrating PID calculation provided in an embodiment of this application;

[0023] Figure 5 This is a schematic diagram of the calculation principle of the PID controller provided in the embodiments of this application;

[0024] Figure 6 This is a schematic diagram of the current balancing control device for an electric arc furnace provided in an embodiment of this application;

[0025] Figure 7 This is a schematic diagram of the terminal provided in the embodiments of this application. Detailed Implementation

[0026] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0028] Figure 1 The implementation flowchart of the current balancing control method for electric arc furnaces provided in the embodiments of this application is described in detail below:

[0029] In S101, the actual values ​​of the three-phase AC current of the three-phase electrodes of the electric arc furnace are obtained.

[0030] This application embodiment applies to a frequency converter, which is connected to the three-phase electrodes of a submerged arc furnace. A schematic diagram of the specific three-phase frequency converter AC submerged arc furnace is provided below. Figure 2 As shown, 21 is a variable frequency power supply converter, 22 is a three-phase electrode, and 23 is a submerged arc furnace. The variable frequency power supply converter 21 is connected to the three-phase electrode 22. The three-phase current can be balanced by adjusting the duty cycle of the switching tube of the variable frequency power supply converter, thereby realizing the automatic adjustment of the submerged arc furnace 23 and achieving stable operation of the submerged arc furnace 23.

[0031] The variable frequency power supply converter adopts space vector pulse width modulation technology and obtains the actual value of the three-phase AC current output by the converter in real time through a current transformer, that is, the actual value of the three-phase AC current is I. A I B I c And it serves as the feedback value for current closed-loop control.

[0032] The main idea of ​​Space Vector Pulse Width Modulation (SVPWM) is to use the ideal flux linkage circle of the stator of a three-phase symmetrical motor under three-phase symmetrical sinusoidal voltage supply as a reference standard. It then uses appropriate switching between different switching modes of the three-phase inverter to generate a PWM wave, and uses the resulting actual flux linkage vector to track its accurate flux linkage circle. Traditional SPWM methods focus on generating a frequency- and voltage-adjustable sinusoidal power supply, while SVPWM considers the inverter system and asynchronous motor as a whole, resulting in a simpler model that is easier for real-time microprocessor control.

[0033] The converter receives the operating current command I SET Including the current setpoint, in this embodiment of the application, the operating current command I related to current closed-loop control... SET It can come from user settings or from the output of the upper-level closed-loop control; the specific settings can be configured according to the actual situation.

[0034] In S102, the actual values ​​of the positive-sequence transformation total current and the negative-sequence current are obtained based on the actual values ​​of the three-phase AC current.

[0035] In one possible implementation, the positive-sequence transformation total current includes the d-axis component and the q-axis component of the positive-sequence transformation total current; the actual value of the negative-sequence current includes the d-axis component and the q-axis component of the negative-sequence current; S102 may include:

[0036] The actual values ​​of the three-phase AC current are transformed by CLARK equal amplitude transformation to obtain the α-axis current signal and β-axis current signal in the αβ two-phase rectangular coordinate system.

[0037] The positive-sequence Park transform converts the α-axis current signal and β-axis current signal into the positive-sequence transform total current d-axis component and the positive-sequence transform total current q-axis component, and the negative-sequence Park transform converts the α-axis current signal and β-axis current signal into the negative-sequence transform total current d-axis component and the negative-sequence transform total current q-axis component.

[0038] Based on the d-axis component and q-axis component of the total negative sequence current, the d-axis component and q-axis component of the negative sequence current are obtained.

[0039] The first step, refer to Figure 3 In this embodiment of the application, the instantaneous power method is used to obtain the actual value of the three-phase AC current in S101 as I. A I B I C After undergoing CLARK equal amplitude transformation, the α-axis current signal I in the αβ two-phase rectangular coordinate system is obtained. α and β-axis current signal I β .

[0040] Among them, the CLARK equal amplitude transformation converts the time-domain components of a three-phase system (in the abc coordinate system) into two components in a two-phase rectangular coordinate system (αβ).

[0041] The specific transformation matrix is ​​shown in formula (1):

[0042]

[0043] The second step involves using a forward-sequence Park transform to convert the α-axis current signal I... α and β-axis current signal I β Transformation into positive sequence transformation of the total current d-axis component and positive sequence transformation of the total current q-axis component

[0044] The negative-order Park transform is used to transform the α-axis current signal I. α and β-axis current signal I β Transformation into negative sequence transformation of the total current d-axis component and negative sequence transformation of the total current q-axis component

[0045] The Park transformation converts two components in the αβ two-phase rectangular coordinate system into two transformations in an orthogonal rotating coordinate system (dq).

[0046] In one possible implementation, using a positive-sequence Park transform to convert the α-axis and β-axis current signals into positive-sequence d-axis and q-axis components of the total current, and using a negative-sequence Park transform to convert the α-axis and β-axis current signals into negative-sequence d-axis and q-axis components of the total current, may include:

[0047] The d-axis component and q-axis component of the total positive-sequence current are calculated using the first formula, which is:

[0048]

[0049] in, To transform the d-axis component of the total current in positive sequence, To transform the q-axis component of the total current in positive sequence, I α For the α-axis current signal, I β This is the β-axis current signal. This is the first coefficient matrix;

[0050] The d-axis component and q-axis component of the total negative-sequence transformation current are calculated using the second formula, which is:

[0051]

[0052] in, To transform the d-axis component of the total current in negative sequence, To transform the q-axis component of the total current in negative sequence, This is the second coefficient matrix.

[0053] The α-axis current signal I is obtained through the first formula. α and β-axis current signal I β Transformation into positive sequence transformation of the total current d-axis component and positive sequence transformation of the total current q-axis component The α-axis current signal I is obtained through the second formula. α and β-axis current signal I β Transformation into negative sequence transformation of the total current d-axis component and negative sequence transformation of the total current q-axis component

[0054] The third step is to transform the d-axis component of the total current according to the negative sequence. and negative sequence transformation of the total current q-axis component Obtain the d-axis component of the negative sequence current and negative sequence current q-axis component

[0055] In one possible implementation, obtaining the d-axis component and q-axis component of the negative-sequence current based on the d-axis component and q-axis component of the negative-sequence transformed total current may include:

[0056] Calculate the transformation values ​​of the first and second matrices based on the third formula;

[0057] Subtracting the first matrix transformation value from the d-axis component of the total negative-sequence transformed current yields the d-axis component of the negative-sequence current; subtracting the second matrix transformation value from the q-axis component of the total negative-sequence transformed current yields the q-axis component of the negative-sequence current.

[0058] The third formula is:

[0059]

[0060] Where Value1 is the value of the first matrix transformation and Value2 is the value of the second matrix transformation. This represents the d-axis component of the negative sequence current. This represents the q-axis component of the negative sequence current. These are the transformation coefficients of the first matrix.

[0061] In this embodiment of the application, the final negative sequence current d-axis component is... and negative sequence current q-axis component The first matrix transformation value Value1 and the second matrix transformation value Value2 are calculated using the third formula; then the negative sequence transformation of the total current d-axis component is performed. Subtracting the first matrix transformation value Value1 yields The negative sequence transformation of the total current q-axis component Subtracting the second matrix transformation value Value2 yields Finally and After passing through a low-pass filter, the negative sequence current d-axis component is output. and negative sequence current q-axis component in, and The calculation formula is shown in formula (2):

[0062]

[0063] The low-pass filter bandwidth configuration in this embodiment can be adjusted to suit the actual effect.

[0064] In this embodiment, the d-axis component of the total current can also be transformed according to the orthogonal sequence. and positive sequence transformation of the total current q-axis component Obtain the d-axis component of the positive sequence current and positive sequence current q-axis component

[0065] Specifically, the d-axis component of the positive sequence current... and positive sequence current q-axis component The transformation values ​​Value3 and Value4 of the third matrix are calculated using formula (3), and then the d-axis components of the total current are transformed in the positive sequence. Subtracting the third matrix transformation value Value3 yields Transform the q-axis component of the total current in the forward sequence. Subtracting the fourth matrix transformation value Value4 yields Finally and After passing through a low-pass filter, the positive-sequence current d-axis component is output. and positive sequence current q-axis component

[0066] Formula (3) is as follows:

[0067]

[0068] in, These are the transformation coefficients of the second matrix.

[0069] and The calculation formula is shown in formula (4):

[0070]

[0071] In S103, a first voltage reference value is obtained by performing PID calculation on the positive sequence transformation total current and the total current setpoint, and a second voltage reference value is obtained by performing PID calculation on the negative sequence current actual value and the negative sequence current setpoint.

[0072] In this embodiment, the current setpoint includes a total current setpoint and a negative sequence current setpoint. The total current setpoint includes the d-axis total current setpoint. and q-axis total current setpoint Negative sequence current setpoints include d-axis negative sequence current setpoints. and q-axis negative sequence current setpoint Among them, the total current setpoint of the d-axis The value is taken as the running current command I. SET , All values ​​are 0.

[0073] In one possible implementation, S103 may include:

[0074] The positive-sequence transformation total current and the total current setpoint are input to the first PID controller, which outputs the positive-sequence transformation total current d-axis output value and the positive-sequence transformation total current q-axis output value. The negative-sequence current actual value and the negative-sequence current setpoint are input to the second PID controller, which outputs the negative-sequence current d-axis output value and the negative-sequence current q-axis output value.

[0075] The positive-sequence Park inverse transformation is performed on the d-axis output value and the q-axis output value of the positive-sequence current to obtain the first voltage reference value, and the negative-sequence current d-axis output value and the negative-sequence current q-axis output value are performed on the negative-sequence Park inverse transformation to obtain the second voltage reference value.

[0076] The positive-sequence transformation total current includes the d-axis component of the positive-sequence transformation total current. and positive sequence transformation of the total current q-axis component The actual value of the negative sequence current includes the d-axis component of the negative sequence current. and negative sequence current q-axis component

[0077] Reference Figure 4 First, transform the d-axis component of the total current in positive sequence. and d-axis total current setpoint Input the first PID controller and calculate the d-axis output value of the total positive current. Transform the q-axis component of the total current in the forward sequence. and q-axis total current setpoint Input the first PID controller and calculate the q-axis output value of the positive transformation total current. The d-axis component of the negative sequence current and d-axis negative sequence current setpoint Input the second PID controller to calculate the d-axis output value of the negative sequence current. The q-axis component of the negative sequence current and q-axis negative sequence current setpoint Input the second PID controller to calculate the q-axis output value of the negative sequence current. in, For running current command I SET The value range is the maximum allowable capacity of the device, for example, it can be set to 1000A. All are set to 0.

[0078] The calculation principle of the PID controller is referred to Figure 5 The calculation formula is as follows: (5)

[0079]

[0080] Among them, I OUT (t) represents the output value, I err(t) represents the error value, K p K is the proportionality coefficient. i K is the integral coefficient. d is the differential coefficient.

[0081] Second, the d-axis output value of the positive transformation total current. The total current q-axis output value of the positive transformation The first voltage reference value is obtained after positive sequence Park inverse transform, and the negative sequence current d-axis output value is obtained. and negative sequence current q-axis output value The second voltage reference value is obtained by performing a negative-order Park inverse transformation.

[0082] In one possible implementation, the first voltage reference value includes a first α-axis voltage reference value and a first β-axis voltage reference value; the second voltage reference value includes a second α-axis voltage reference value and a second β-axis voltage reference value.

[0083] The first voltage reference value can be obtained by performing a forward-sequence Park inverse transform on the d-axis output value of the forward-transformed total current and the q-axis output value of the forward-transformed total current.

[0084] The first α-axis voltage reference value and the first β-axis voltage reference value are calculated using the fourth formula, which is:

[0085]

[0086] Among them, U α (t) is the first α-axis voltage reference, U β (t) is the first β-axis voltage reference value. This represents the d-axis output value of the total current during positive transformation. This represents the q-axis output value of the total current during positive transformation. These are the coefficients of the first inverse transform;

[0087] The second voltage reference value can be obtained by performing an inverse negative-sequence Park transformation on the negative-sequence current d-axis output value and the negative-sequence current q-axis output value.

[0088] The second α-axis voltage reference value and the second β-axis voltage reference value are calculated using the fifth formula, which is:

[0089]

[0090] in, This is the reference value for the second α-axis voltage. This is the reference value for the second β-axis voltage. This is the d-axis output value of the negative sequence current. This is the q-axis output value for the negative sequence current. These are the coefficients of the second inverse transform.

[0091] In this embodiment of the application, the first voltage reference value includes a first α-axis voltage reference value and a first β-axis voltage reference value; the second voltage reference value includes a second α-axis voltage reference value and a second β-axis voltage reference value.

[0092] Then the positive transformation of the total current d-axis output value will be... The total current q-axis output value of the positive transformation The first α-axis voltage reference value U is obtained after the forward-order Park inverse transform. α (t) and the first β-axis voltage reference value U β (t) will output the negative sequence current d-axis value. and negative sequence current q-axis output value The second α-axis voltage reference value is obtained after negative-sequence Park inverse transform. Second β-axis voltage reference value

[0093] In S104, the duty cycle signal for controlling the frequency converter is generated using the first voltage reference value and the second voltage reference value.

[0094] According to S103, the first voltage reference value includes the first α-axis voltage reference value and the first β-axis voltage reference value; the second voltage reference value includes the second α-axis voltage reference value and the second β-axis voltage reference value.

[0095] In one possible implementation, S104 may include:

[0096] The sum of the first α-axis voltage reference value and the second α-axis voltage reference value, as well as the sum of the first β-axis voltage reference value and the second β-axis voltage reference value, are input into the SVPWM pulse generator, and the duty cycle signal of the frequency converter is output.

[0097] The first α-axis voltage reference value U is obtained according to the summation calculation formula (6). α (t) and the second α-axis voltage reference value and and the first β-axis voltage reference value U β (t) and the second β-axis voltage reference value and Will and Input the SVPWM pulse generator to complete the pulse width calculation and output the duty cycle signal of the frequency converter.

[0098] In this embodiment, the three-phase current of the three-phase electrodes is adjusted by regulating the duty cycle signal, so that the three-phase current of the electric arc furnace is output in a balanced manner, realizing automatic adjustment, reducing human intervention, and improving the adjustment response speed. By making the three-phase current output the same, the balance of three-phase power is ensured, and the operational stability of the electric arc furnace is improved. Furthermore, by balancing the output of the three-phase current, the influence of negative sequence current is suppressed, the impact on the power grid is reduced, and the power quality is improved.

[0099] Formula (6) is as follows:

[0100]

[0101] This application provides a current balancing control method for an electric arc furnace (EAF). The method involves obtaining the actual values ​​of the three-phase AC currents of the three-phase electrodes of the EAF; obtaining the actual values ​​of the positive-sequence total current and the negative-sequence current based on these actual values; performing PID calculations on the positive-sequence total current and the given current value to obtain a first voltage reference value; and performing PID calculations on the actual value of the negative-sequence current and the given current value to obtain a second voltage reference value; and using the first and second voltage reference values ​​to generate a duty cycle signal for controlling the variable frequency power supply converter. This application uses a variable frequency power supply converter to achieve balanced three-phase current output, avoiding the negative-sequence current problem caused by three-phase current imbalance in traditional transformer-type power supply systems, improving the power quality of the power supply system, and reducing the negative impact of the system on the power grid.

[0102] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0103] The following are device embodiments of this application. For details not described in detail, please refer to the corresponding method embodiments described above.

[0104] Figure 6 A schematic diagram of the current balancing control device for an electric arc furnace provided in an embodiment of this application is shown. For ease of explanation, only the parts relevant to the embodiment of this application are shown, and are described in detail below:

[0105] like Figure 6 As shown, the current balancing control device 6 for the electric arc furnace includes:

[0106] The acquisition module 61 is used to acquire the actual value of the three-phase AC current of the three-phase electrodes of the electric arc furnace;

[0107] The first calculation module 62 is used to obtain the actual values ​​of the positive sequence transformation total current and the negative sequence current based on the actual values ​​of the three-phase AC current.

[0108] The second calculation module 63 is used to perform PID calculation on the positive sequence transformation total current and the total current setpoint to obtain the first voltage reference value, and to perform PID calculation on the negative sequence current actual value and the negative sequence current setpoint to obtain the second voltage reference value.

[0109] The generation module 64 is used to generate a duty cycle signal for controlling the frequency converter using a first voltage reference value and a second voltage reference value.

[0110] This application provides a current balancing control device for an electric arc furnace (EAF). It acquires the actual values ​​of the three-phase AC currents of the three-phase electrodes of the EAF; obtains the actual values ​​of the positive-sequence total current and the negative-sequence current based on the actual values ​​of the three-phase AC currents; performs PID calculations on the positive-sequence total current and the total current setpoint to obtain a first voltage reference value, and performs PID calculations on the actual value of the negative-sequence current and the negative-sequence current setpoint to obtain a second voltage reference value; and uses the first and second voltage reference values ​​to generate a duty cycle signal for controlling the frequency converter. This application uses a frequency converter to achieve three-phase current balancing output, avoiding the negative-sequence current problem caused by three-phase current imbalance in traditional transformer-type power supply systems, improving the power quality of the power supply system, and reducing the negative impact of the system on the power grid.

[0111] In one possible implementation, the positive-sequence transformation total current includes the d-axis component and the q-axis component of the positive-sequence transformation total current; the actual value of the negative-sequence current includes the d-axis component and the q-axis component of the negative-sequence current; the first calculation module can specifically be used for:

[0112] The actual values ​​of the three-phase AC current are transformed by CLARK equal amplitude transformation to obtain the α-axis current signal and β-axis current signal in the αβ two-phase rectangular coordinate system.

[0113] The positive-sequence Park transform converts the α-axis current signal and β-axis current signal into the positive-sequence transform total current d-axis component and the positive-sequence transform total current q-axis component, and the negative-sequence Park transform converts the α-axis current signal and β-axis current signal into the negative-sequence transform total current d-axis component and the negative-sequence transform total current q-axis component.

[0114] Based on the d-axis component and q-axis component of the total negative sequence current, the d-axis component and q-axis component of the negative sequence current are obtained.

[0115] In one possible implementation, the first computing module can also be used for:

[0116] The d-axis component and q-axis component of the total positive-sequence current are calculated using the first formula, which is:

[0117]

[0118] in, To transform the d-axis component of the total current in positive sequence, To transform the q-axis component of the total current in positive sequence, I α For the α-axis current signal, I β This is the β-axis current signal. This is the first coefficient matrix;

[0119] The d-axis component and q-axis component of the total negative-sequence transformation current are calculated using the second formula, which is:

[0120]

[0121] in, To transform the d-axis component of the total current in negative sequence, To transform the q-axis component of the total current in negative sequence, This is the second coefficient matrix.

[0122] In one possible implementation, the first computing module can also be used for:

[0123] Calculate the transformation values ​​of the first and second matrices based on the third formula;

[0124] Subtracting the first matrix transformation value from the d-axis component of the total negative-sequence transformed current yields the d-axis component of the negative-sequence current; subtracting the second matrix transformation value from the q-axis component of the total negative-sequence transformed current yields the q-axis component of the negative-sequence current.

[0125] The third formula is:

[0126]

[0127] Where Value1 is the value of the first matrix transformation and Value2 is the value of the second matrix transformation. This represents the d-axis component of the negative sequence current. This represents the q-axis component of the negative sequence current. These are the transformation coefficients of the first matrix.

[0128] In one possible implementation, the second computation module can specifically be used for:

[0129] The positive-sequence transformation total current and the total current setpoint are input to the first PID controller, which outputs the positive-sequence transformation total current d-axis output value and the positive-sequence transformation total current q-axis output value. The negative-sequence current actual value and the negative-sequence current setpoint are input to the second PID controller, which outputs the negative-sequence current d-axis output value and the negative-sequence current q-axis output value.

[0130] The positive-sequence Park inverse transformation is performed on the d-axis output value and the q-axis output value of the positive-sequence current to obtain the first voltage reference value, and the negative-sequence current d-axis output value and the negative-sequence current q-axis output value are performed on the negative-sequence Park inverse transformation to obtain the second voltage reference value.

[0131] In one possible implementation, the first voltage reference value includes a first α-axis voltage reference value and a first β-axis voltage reference value; the second voltage reference value includes a second α-axis voltage reference value and a second β-axis voltage reference value.

[0132] The second calculation module can also be used for:

[0133] The first α-axis voltage reference value and the first β-axis voltage reference value are calculated using the fourth formula, which is:

[0134]

[0135] Among them, U α (t) is the first α-axis voltage reference, U β (t) is the first β-axis voltage reference value. This represents the d-axis output value of the total current during positive transformation. This represents the q-axis output value of the total current during positive transformation. These are the coefficients of the first inverse transform;

[0136] The second calculation module can also be used for:

[0137] The second α-axis voltage reference value and the second β-axis voltage reference value are calculated using the fifth formula, which is:

[0138]

[0139] in, This is the reference value for the second α-axis voltage. This is the reference value for the second β-axis voltage. This is the d-axis output value of the negative sequence current. This is the q-axis output value for the negative sequence current. These are the coefficients of the second inverse transform.

[0140] In one possible implementation, the generation module can specifically be used for:

[0141] The sum of the first α-axis voltage reference value and the second α-axis voltage reference value, as well as the sum of the first β-axis voltage reference value and the second β-axis voltage reference value, are input into the SVPWM pulse generator, and the duty cycle signal of the frequency converter is output.

[0142] Figure 7 This is a schematic diagram of the terminal provided in an embodiment of this application. For example... Figure 7As shown, the terminal 7 in this embodiment includes: a processor 70, a memory 71, and a computer program 72 stored in the memory 71 and executable on the processor 70. When the processor 70 executes the computer program 72, it implements the steps in the various embodiments of the electric arc furnace current balancing control method described above, for example... Figure 1 S101 to S104 are shown. Alternatively, when the processor 70 executes the computer program 72, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 6 The functions of modules 61 to 64 are shown.

[0143] For example, the computer program 72 can be divided into one or more modules / units, which are stored in the memory 71 and executed by the processor 70 to complete this application. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 72 in the terminal 7. For example, the computer program 72 can be divided into... Figure 6 Modules 61 to 64 are shown.

[0144] The terminal 7 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The terminal 7 may include, but is not limited to, a processor 70 and a memory 71. Those skilled in the art will understand that... Figure 7 This is merely an example of terminal 7 and does not constitute a limitation on terminal 7. It may include more or fewer components than shown, or combine certain components, or different components. For example, the terminal may also include input / output devices, network access devices, buses, etc.

[0145] The processor 70 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0146] The memory 71 can be an internal storage unit of the terminal 7, such as a hard disk or memory of the terminal 7. The memory 71 can also be an external storage device of the terminal 7, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal 7. Furthermore, the memory 71 can include both internal storage units and external storage devices of the terminal 7. The memory 71 is used to store the computer program and other programs and data required by the terminal. The memory 71 can also be used to temporarily store data that has been output or will be output.

[0147] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0148] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0149] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0150] In the embodiments provided in this application, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0151] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0152] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0153] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above-described embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various embodiments of the submerged arc furnace current balancing control method. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content contained in the computer-readable medium may be appropriately added to or subtracted from the content as required by the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium may not include electrical carrier signals and telecommunication signals.

[0154] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A current equalization control method for a submerged arc furnace, characterized in that, The method is applied to a variable frequency power supply converter, which is connected to the three-phase electrodes of a submerged arc furnace. The method includes: Obtain the actual value of the three-phase alternating current of the three-phase electrodes of the electric arc furnace; The actual values ​​of the positive-sequence transformation total current and the negative-sequence current are obtained based on the actual values ​​of the three-phase AC current. The positive-sequence transformation total current includes the d-axis component and the q-axis component of the positive-sequence transformation total current. The actual values ​​of the negative-sequence current include the d-axis component and the q-axis component of the negative-sequence transformation total current. A first voltage reference value is obtained by performing PID calculation on the positive sequence transformation total current and the total current setpoint, and a second voltage reference value is obtained by performing PID calculation on the negative sequence current actual value and the negative sequence current setpoint. The duty cycle signal for controlling the frequency converter is generated using the first voltage reference value and the second voltage reference value. The method further includes, after obtaining the actual values ​​of the positive-sequence transformation total current and the negative-sequence current based on the actual values ​​of the three-phase AC current, the method further includes: Based on the d-axis component and the q-axis component of the total negative sequence current, the d-axis component and the q-axis component of the negative sequence current are obtained. Based on the d-axis component and q-axis component of the positive-sequence transformed total current, the d-axis component and q-axis component of the positive-sequence transformed total current are obtained. The step of performing PID calculations on the positive-sequence transformation total current and the total current setpoint to obtain a first voltage reference value, and performing PID calculations on the negative-sequence current actual value and the negative-sequence current setpoint to obtain a second voltage reference value, includes: The positive-sequence total current and the given value of the total current are input to the first PID controller, which outputs the d-axis output value and the q-axis output value of the positive-sequence total current. The actual value of the negative-sequence current and the given value of the negative-sequence current are input to the second PID controller, which outputs the d-axis output value and the q-axis output value of the negative-sequence current. The first voltage reference value is obtained by performing a positive-sequence Park inverse transformation on the d-axis output value and the q-axis output value of the positive-sequence current, and the second voltage reference value is obtained by performing a negative-sequence Park inverse transformation on the d-axis output value and the q-axis output value of the negative-sequence current.

2. The current equalization control method for a submerged arc furnace according to claim 1, characterized in that, The step of obtaining the actual values ​​of the positive-sequence transformation total current and the negative-sequence current based on the actual values ​​of the three-phase AC current includes: The actual value of the three-phase AC current is obtained by performing a Clark equal-amplitude transformation. Two-phase rectangular coordinate system shaft current signal and Shaft current signal; The orthogonal Park transformation is used to transform the above shaft current signal and the The d-axis current signal is transformed into the positive-sequence transformed total current d-axis component and the positive-sequence transformed total current q-axis component, and then the negative-sequence Park transform is used to transform the signal. shaft current signal and the The axis current signal is transformed into the negative-sequence transformed total current d-axis component and the negative-sequence transformed total current q-axis component.

3. The current equalization control method for a submerged arc furnace according to claim 2, characterized in that, The above uses the orthogonal Park transformation to... shaft current signal and the The d-axis current signal is transformed into the positive-sequence transformed total current d-axis component and the positive-sequence transformed total current q-axis component, and then the negative-sequence Park transform is used to transform the signal. shaft current signal and the The transformation of the d-axis component and q-axis component of the negative-sequence total current signal into the negative-sequence total current includes: The d-axis component and q-axis component of the positive-sequence transformation total current are calculated using the first formula, which is: in, The d-axis component of the total current of the positive-sequence transformation. Let q be the q-axis component of the total current in the positive-sequence transformation. For the shaft current signal, For the shaft current signal, This is the first coefficient matrix; The d-axis component and q-axis component of the total negative-sequence transformed current are calculated using the second formula, which is: in, The negative-sequence transformation total current d-axis component, The negative-sequence transformation total current q-axis component is... This is the second coefficient matrix.

4. The current equalization control method for a submerged arc furnace according to claim 2, characterized in that, The step of obtaining the d-axis component and q-axis component of the negative-sequence current based on the d-axis component and q-axis component of the negative-sequence transformed total current includes: Calculate the transformation values ​​of the first and second matrices based on the third formula; The negative sequence current d-axis component is obtained by subtracting the first matrix transformation value from the negative sequence total current d-axis component, and the negative sequence current q-axis component is obtained by subtracting the second matrix transformation value from the negative sequence total current q-axis component. The third formula is as follows: in, The transformation value of the first matrix. The value of the second matrix transformation. The negative sequence current is represented by its d-axis component. This refers to the q-axis component of the negative sequence current. These are the transformation coefficients of the first matrix.

5. The current equalization control method for a submerged arc furnace according to claim 1, characterized in that, The first voltage reference value includes the first Shaft voltage reference value and first Shaft voltage reference value; the second voltage reference value includes the second Shaft voltage reference value and second Shaft voltage reference value; The step of obtaining the first voltage reference value by performing a forward-sequence Park inverse transformation on the d-axis output value of the forward-transformed total current and the q-axis output value of the forward-transformed total current includes: The first one is obtained by calculating using the fourth formula. Shaft voltage reference value and the first The shaft voltage reference value, the fourth formula is: in, For the first Shaft voltage reference, For the first Shaft voltage reference value, This represents the d-axis output value of the total positive transformation current. This represents the q-axis output value of the total positive transformation current. These are the coefficients of the first inverse transform; The step of obtaining the second voltage reference value by performing a negative-sequence current d-axis output value and a negative-sequence current q-axis output value through a negative-sequence Park inverse transformation includes: The second result is obtained by calculating using the fifth formula. Shaft voltage reference value and the second The shaft voltage reference value, the fifth formula is: in, For the second Shaft voltage reference value, For the second Shaft voltage reference value, This is the d-axis output value of the negative sequence current. This is the q-axis output value of the negative sequence current. These are the coefficients of the second inverse transform.

6. The current equalization control method for a submerged arc furnace according to claim 5, characterized in that, The step of generating the duty cycle signal for controlling the frequency converter using the first voltage reference value and the second voltage reference value includes: The first Shaft voltage reference value and the second The sum of the shaft voltage reference values, and the first Shaft voltage reference value and the second The shaft voltage reference value is input to the SVPWM pulse generator, which outputs the duty cycle signal of the frequency converter.

7. A current balancing control device for a submerged arc furnace, characterized in that, include: The acquisition module is used to acquire the actual value of the three-phase AC current of the three-phase electrodes of the electric arc furnace. The first calculation module is used to obtain the actual values ​​of the positive-sequence transformation total current and the negative-sequence current based on the actual values ​​of the three-phase AC current. The positive-sequence transformation total current includes the d-axis component and the q-axis component of the positive-sequence transformation total current; the actual value of the negative-sequence current includes the d-axis component and the q-axis component of the negative-sequence transformation total current. The second calculation module is used to perform PID calculation on the positive sequence transformation total current and the total current given value to obtain a first voltage reference value, and to perform PID calculation on the negative sequence current actual value and the negative sequence current given value to obtain a second voltage reference value. The generation module is used to generate a duty cycle signal for controlling the frequency converter using the first voltage reference value and the second voltage reference value; Wherein, after the first computing module, the device is further configured to: Based on the d-axis component and the q-axis component of the total negative sequence current, the d-axis component and the q-axis component of the negative sequence current are obtained. Based on the d-axis component and q-axis component of the positive-sequence transformed total current, the d-axis component and q-axis component of the positive-sequence transformed total current are obtained. The second calculation module is used for: The positive-sequence total current and the given value of the total current are input to the first PID controller, which outputs the d-axis output value and the q-axis output value of the positive-sequence total current. The actual value of the negative-sequence current and the given value of the negative-sequence current are input to the second PID controller, which outputs the d-axis output value and the q-axis output value of the negative-sequence current. The first voltage reference value is obtained by performing a positive-sequence Park inverse transformation on the d-axis output value and the q-axis output value of the positive-sequence current, and the second voltage reference value is obtained by performing a negative-sequence Park inverse transformation on the d-axis output value and the q-axis output value of the negative-sequence current.

8. A terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the current equalization control method for an electric arc furnace as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the current equalization control method for an electric arc furnace as described in any one of claims 1 to 6.

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