Parallel resonant power factor angle adaptive control method and system

Abstract

The present disclosure provides a parallel resonant power factor angle adaptive control method and system, comprising: acquiring current load current lead angle, inverter frequency, inverter voltage, DC current value and preset value of commutation inductance parameter in real time; obtaining the intermediate frequency voltage value at the commutation time based on the product of the current load current lead angle and the inverter voltage; and obtaining the commutation time based on the ratio of the obtained DC current value and the commutation inductance to the intermediate frequency voltage value at the commutation time; when the intermediate frequency voltage value is less than a preset threshold, the load current lead angle is assigned a preset constant; otherwise, the following steps are performed: judging whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse pressure off time, when the condition is met, the current lead angle is reduced, and the judgment is re-performed; when the preset condition is not met, the current lead angle is increased until the condition is met.

Description

Technical Field

[0001] This disclosure belongs to the field of thyristor parallel resonant intermediate frequency furnace control technology, and particularly relates to a parallel resonant power factor angle adaptive control method and system. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] In a thyristor parallel resonant intermediate frequency furnace, the output current needs to lead the output voltage by a certain angle φ to ensure successful commutation (the thyristor parallel resonant circuit is a current-source inverter circuit; since the thyristor is a semi-controlled device, the circuit operates using load commutation, requiring the load current to slightly lead the load voltage). This angle φ is also called the load current lead angle, and the corresponding time is the load current lead time T. f To ensure reliable commutation, T f It must be greater than the commutation time T α With the reverse voltage turn-off time T of the components β The sum of these factors. In the initial stage of smelting, the input impedance is low; in the initial startup stage, the frequency is low and the intermediate frequency voltage is low while the input current is high. Therefore, a commutation time T is required. α and shutdown time T β Both are relatively large; under the condition of full power output of the hot furnace, the intermediate frequency voltage is high, the frequency is high, and the input impedance is large. At this time, the commutation time T α and shutdown time T β They all got smaller.

[0004] Based on the above characteristics, most products on the market currently use a fixed load current lead angle for control. This control method can meet most operating conditions, but it has the following problems:

[0005] (1) During heavy-load startup conditions after the furnace is newly built (i.e., the inner wall of the electric furnace is made of refractory material), i.e., the furnace is frozen and the first furnace is cold, which is the worst startup condition, the load current lead time T is very low due to the very low input impedance. f The angle needs to be increased further, so the commissioning personnel can only adjust the load current lead angle φ of normal operation to meet the time required for this condition. However, most of the operating time is still under conditions of high impedance. This method will result in a low power factor. If the large lead angle is maintained, it will lead to high thyristor commutation voltage, high losses, and a low power factor, resulting in low utilization of system current and voltage.

[0006] (2) The design frequency of the smelting furnace ranges from hundreds to thousands of hertz. The commissioning personnel need to manually determine the φ value according to the working conditions of each furnace, which makes the commissioning complicated, relies too much on human experience, and there is a certain risk of commutation failure in the system operation. Summary of the Invention

[0007] To address the aforementioned issues, this disclosure provides a parallel resonant power factor angle adaptive control method and system. The scheme employs disturbance detection to dynamically adjust the load current lead angle, effectively improving the utilization rate of the system current and voltage.

[0008] According to a first aspect of the present disclosure, a method for adaptive control of the angle of a parallel resonant power factor is provided, comprising:

[0009] Real-time acquisition of current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters;

[0010] Based on the product of the current load current lead angle and the inverter voltage, the intermediate frequency voltage value at the commutation moment is obtained; and based on the obtained DC current value and the ratio of the commutation inductance to the intermediate frequency voltage value at the commutation moment, the commutation time is obtained.

[0011] When the intermediate frequency voltage value is less than a preset threshold, the load current lead angle is assigned a preset constant value; otherwise, the following steps are performed: determine whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time. If the condition is met, the current lead angle is reduced and the judgment is performed again; if the preset condition is not met, the current lead angle is increased until the condition is met.

[0012] Furthermore, the intermediate frequency voltage value at the commutation moment is obtained based on the product of the current load current lead angle and the inverter voltage, specifically using the following formula:

[0013]

[0014] Where Urms is the inverter voltage sampling value, and φ is the current load current lead angle.

[0015] Furthermore, the commutation time is obtained based on the ratio of the obtained DC current value and the commutation inductance to the intermediate frequency voltage value at the commutation moment, specifically using the following formula:

[0016]

[0017] Among them, T α For commutation time, I d For direct current, L k U0 is the commutation inductor, and U0 is the intermediate frequency voltage value.

[0018] Furthermore, the determination of whether the lead time corresponding to the lead angle of the current load current is greater than the sum of the commutation time and the reverse voltage turn-off time introduces a delay compensation time based on the sum of the commutation time and the reverse voltage turn-off time.

[0019] Furthermore, when the condition is met, the current lead angle is reduced and a new judgment is made; when the preset condition is not met, the current lead angle is increased until the condition is met; the adjustment of the lead angle is specifically achieved by changing the phase difference between the current and the voltage by adjusting the triggering time of the SCR.

[0020] According to a second aspect of the present disclosure, a parallel resonant power factor angle adaptive control system is provided, comprising:

[0021] The data acquisition unit is used to acquire the current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters in real time.

[0022] The intermediate frequency voltage and commutation time determination unit is used to obtain the intermediate frequency voltage value at the commutation time based on the product of the current load current lead angle and the inverter voltage; and to obtain the commutation time based on the obtained DC current value and the ratio of the commutation inductance to the intermediate frequency voltage value at the commutation time.

[0023] The lead angle determination unit is used to assign a preset constant to the load current lead angle when the intermediate frequency voltage value is less than a preset threshold; otherwise, it performs the following steps: determining whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time; if the condition is met, the current lead angle is reduced and the determination is repeated; if the preset condition is not met, the current lead angle is increased until the condition is met.

[0024] According to a third aspect of the present disclosure, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and running on the memory, wherein the processor executes the program to implement the aforementioned parallel resonant power factor angle adaptive control method.

[0025] According to a fourth aspect of the present disclosure, a non-transitory computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the aforementioned parallel resonant power factor angle adaptive control method.

[0026] Compared with the prior art, the beneficial effects of this disclosure are:

[0027] (1) This disclosure provides a parallel resonant power factor angle adaptive control method and system. The scheme adopts a disturbance detection method to dynamically adjust the load current lead angle. Specifically, by quantifying the commutation time and the turn-off time, the lead time is accurately estimated. The load current lead time is dynamically adjusted according to the value of AC impedance to replace the traditional fixed load current lead angle control method, which effectively improves the utilization rate of system current and voltage.

[0028] (2) The proposed scheme intelligently distinguishes between cold furnace start-up and hot furnace start-up (i.e., heavy load start-up and light load start-up) based on AC impedance, and implements different processing mechanisms for different operating conditions. Heavy load generally occurs when the first batch of cold material is added after the furnace is heated. These can be determined by the ratio of input voltage to input current, which is the input impedance. Under heavy load, the input current is high and the input voltage is very low. Under light load, the input current and input voltage are basically proportional to the maximum range. By distinguishing different operating conditions and processing them separately, the utilization rate of system current and voltage can be further improved.

[0029] Advantages of this disclosure in additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0030] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure.

[0031] Figure 1 This is a flowchart of a parallel resonant power factor angle adaptive control method as described in an embodiment of this disclosure;

[0032] Figure 2 This is a schematic diagram of the thyristor parallel resonant circuit structure described in the embodiments of this disclosure. Detailed Implementation

[0033] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] Where there is no conflict, the embodiments and features described herein can be combined with each other.

[0037] Terminology Explanation:

[0038] Lead time: This refers to the time during which the load voltage leads the load current. The load current lead time and lead angle are the same concept. Utilizing the fixed frequency characteristic of intermediate frequency voltage, the two can be converted to each other. It is simply a formula for converting angle to time.

[0039] Example 1:

[0040] The purpose of this embodiment is to provide a method for adaptive control of the angle of parallel resonant power factor.

[0041] like Figure 1 As shown, a parallel resonant power factor angle adaptive control method includes:

[0042] Real-time acquisition of current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters;

[0043] Based on the product of the current load current lead angle and the inverter voltage, the intermediate frequency voltage value at the commutation moment is obtained; and based on the obtained DC current value and the ratio of the commutation inductance to the intermediate frequency voltage value at the commutation moment, the commutation time is obtained.

[0044] When the intermediate frequency voltage value is less than a preset threshold, the load current lead angle is assigned a preset constant value; otherwise, the following steps are performed: determine whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time. If the condition is met, the current lead angle is reduced and the judgment is performed again; if the preset condition is not met, the current lead angle is increased until the condition is met.

[0045] Furthermore, the intermediate frequency voltage value at the commutation moment is obtained based on the product of the current load current lead angle and the inverter voltage, specifically using the following formula:

[0046]

[0047] Where Urms is the inverter voltage sampling value, and φ is the current load current lead angle.

[0048] Furthermore, the commutation time is obtained based on the ratio of the obtained DC current value and the commutation inductance to the intermediate frequency voltage value at the commutation moment, specifically using the following formula:

[0049]

[0050] Among them, T α For commutation time, I d For direct current, L k U0 is the commutation inductor, and U0 is the intermediate frequency voltage value.

[0051] Furthermore, the determination of whether the lead time corresponding to the lead angle of the current load current is greater than the sum of the commutation time and the reverse voltage turn-off time introduces a delay compensation time based on the sum of the commutation time and the reverse voltage turn-off time.

[0052] Furthermore, when the condition is met, the current lead angle is reduced and a new judgment is made; when the preset condition is not met, the current lead angle is increased until the condition is met. The adjustment of the lead angle is as follows: since it is working in a resonant state, the frequency of the inverter voltage is constant, so the lead angle can be modified by simply adjusting the triggering time of the SCR to change the phase difference between the current and the voltage.

[0053] Furthermore, when the intermediate frequency voltage value is less than a preset threshold, the load current lead angle is assigned a preset constant. Specifically, the preset constant is set by the human-machine interface according to the field conditions. Generally, the intermediate frequency voltage value is set to about 30%-50% of the full scale, and the angle is limited to the maximum angle that the human-machine interface can set.

[0054] Specifically, for ease of understanding, the solution described in this disclosure will be explained in detail below with reference to the accompanying drawings:

[0055] like Figure 1 As shown, this disclosure provides a parallel resonant power factor angle adaptive control method. The scheme still uses the load current leading angle for phase-locked control, that is, the angle φ is dynamically adjusted by disturbance detection. The specific steps are as follows:

[0056] Step 1: Real-time acquisition of the current load current lead angle φ, inverter frequency, inverter voltage sampling value Urms, DC current value, and preset values ​​of commutator inductor parameters; among which, the inverter frequency is measured based on the inverter voltage and belongs to the system's resonant frequency, which is related to the inductor coil and resonant capacitor; the inverter voltage is the voltage output by the inverter applied to the coil, which is acquired through a voltage transformer.

[0057] Step 2: Based on formula (1), calculate the intermediate frequency voltage U at the commutation moment according to the current load current lead angle φ, inverter frequency, inverter voltage sampling value Urms, DC current value, and preset values ​​of commutator inductor parameters. o and commutation time T α ;

[0058]

[0059]

[0060] Where: Urms is the inverter voltage sampling value, φ is the current load current lead angle; I d It is a direct current, which can be obtained by DC Hall sampling; Lk T is the commutation inductance, a system-specific parameter determined during main circuit design; U0 is the intermediate frequency voltage at commutation, which can be obtained directly from AC sampling by the CPU or calculated based on the root mean square value of the intermediate frequency voltage and the commutation angle; T α The commutation time is calculated from the parameters mentioned above.

[0061] Step 3: Perform segmentation based on the obtained intermediate frequency voltage:

[0062] When the intermediate frequency voltage is lower than the set limit U low Going forward, the angle φ will be limited to a relatively large value. max Firstly, the intermediate frequency voltage is low under these conditions, which will affect the sampling accuracy. According to the above formula, there will be some deviation. Secondly, the output power is generally small and the output voltage is also low under these conditions. Moreover, this condition only accounts for a small part of the entire melting process. Therefore, a larger angle will not bring too much loss and can increase the stability and robustness of the system.

[0063] When it is not lower than the set limit U low At that time, the reverse voltage turn-off time T is obtained by referring to the table corresponding to the reverse voltage time curves provided in the U0 and SCR component datasheets. β Verify T α +T β Does the difference between the time value T1 corresponding to the angle φ and the time value T1 satisfy T1>T? α +T β +T tot Among them, T tot This is a delay compensation time to compensate for component parameter deviations and ensure automatic adjustment margin. Ttot is the delay compensation time for compensating for component parameter deviations and ensuring automatic adjustment margin. It is a parameter preset by the on-site commissioning personnel, generally defined by angle, and can be set on-site through the HMI (Human Machine Interface). It is typically set to 1-2 degrees on-site. When the T1 value meets the above conditions, the angle φ is further reduced and the judgment is re-evaluated. If the T1 value does not meet the conditions, the angle φ is increased until the conditions are met. This method can dynamically adapt to changes in impedance and resonant frequency, ensuring the resonant circuit always operates in a state of high power factor and low turn-off loss, improving melting efficiency and increasing melting speed.

[0064] Furthermore, such as Figure 2The diagram shows a parallel resonant circuit with thyristors, which is a current-source inverter circuit. Since thyristors are semi-controlled devices, the circuit operates using a load commutation method, requiring the load current to slightly lead the load voltage. In the diagram, Ld is a DC inductor that ensures the constant current characteristic of the input. VT1-VT4 are four sets of inverter thyristors that form an inverter bridge. LT1-LT4 are commutation inductors used to limit the di / dt of the thyristors when they are turned on. L, R, and C are the inductor, equivalent resistance, and compensation capacitor, respectively.

[0065] Example 2:

[0066] The purpose of this embodiment is to provide a parallel resonant power factor angle adaptive control system.

[0067] A parallel resonant power factor angle adaptive control system, comprising:

[0068] The data acquisition unit is used to acquire the current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters in real time.

[0069] The intermediate frequency voltage and commutation time determination unit is used to obtain the intermediate frequency voltage value at the commutation time based on the product of the current load current lead angle and the inverter voltage; and to obtain the commutation time based on the obtained DC current value and the ratio of the commutation inductance to the intermediate frequency voltage value at the commutation time.

[0070] The lead angle determination unit is used to assign a preset constant to the load current lead angle when the intermediate frequency voltage value is less than a preset threshold; otherwise, it performs the following steps: determining whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time; if the condition is met, the current lead angle is reduced and the determination is repeated; if the preset condition is not met, the current lead angle is increased until the condition is met.

[0071] Furthermore, the system described in this embodiment corresponds to the method described in Embodiment 1, and its technical details have been described in Embodiment 1, so they will not be repeated here.

[0072] In further embodiments, the following is also provided:

[0073] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When executed by the processor, the computer instructions perform the method described in Embodiment 1. For brevity, further details are omitted here.

[0074] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0075] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0076] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the method described in Embodiment 1.

[0077] The method in Embodiment 1 can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor. The software modules can reside in readily available storage media in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory; the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, a detailed description is not provided here.

[0078] Those skilled in the art will recognize that the units, i.e., algorithm steps, of the various examples described in connection with this embodiment 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 disclosure.

[0079] The parallel resonant power factor angle adaptive control method and system provided in the above embodiments can be implemented and has broad application prospects.

[0080] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A parallel resonant power factor angle adaptive control method, characterized by, include: Real-time acquisition of current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters; The intermediate frequency voltage value at the commutation moment is obtained by multiplying the current load current lead angle and the inverter voltage, using the following formula: Where Urms is the inverter voltage. The leading angle is determined by the current load current; and the commutation time is obtained based on the ratio of the obtained DC current value and the commutation inductance to the intermediate frequency voltage value at the commutation moment, specifically using the following formula: Among them, T α For commutation time, I d L is the DC current value. k The parameters of the commutation inductor are preset values, and U0 is the intermediate frequency voltage value; When the intermediate frequency voltage value is less than a preset threshold, the load current lead angle is assigned a preset constant value, which is the maximum allowable lead angle of the current load current set through the human-machine interface; otherwise, the following steps are performed: determine whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time. If the condition is met, the current lead angle is reduced; if the preset condition is not met, the current lead angle is increased.

2. The parallel resonant power factor angle adaptive control method as described in claim 1, characterized in that, The determination of whether the lead time corresponding to the lead angle of the current load current is greater than the sum of the commutation time and the reverse voltage turn-off time involves introducing a delay compensation time based on the sum of the commutation time and the reverse voltage turn-off time.

3. The parallel resonant power factor angle adaptive control method as described in claim 1, characterized in that, When the conditions are met, the current lead angle is reduced; when the preset conditions are not met, the current lead angle is increased. The adjustment of the lead angle is specifically achieved by changing the phase difference between the current and the voltage by adjusting the triggering time of the SCR.

4. A parallel resonant power factor angle adaptive control system, characterized by, include: The data acquisition unit is used to acquire the current load current lead angle, inverter frequency, inverter voltage, DC current value, and preset values ​​of commutator inductor parameters in real time. The intermediate frequency voltage and commutation time determination unit is used to obtain the intermediate frequency voltage value at the commutation time based on the product of the current load current lead angle and the inverter voltage, specifically using the following formula: Where Urms is the inverter voltage. The leading angle is determined by the current load current; and the commutation time is obtained based on the ratio of the obtained DC current value and the commutation inductance to the intermediate frequency voltage value at the commutation moment, specifically using the following formula: Among them, T α For commutation time, I d L is the DC current value. k The parameters of the commutation inductor are preset values, and U0 is the intermediate frequency voltage value; The lead angle determination unit is used to assign a preset constant to the load current lead angle when the intermediate frequency voltage value is less than a preset threshold. The preset constant is the maximum allowable lead angle of the current load current set through the human-machine interface. Otherwise, the following steps are performed: it is determined whether the lead time corresponding to the current load current lead angle is greater than the sum of the commutation time and the reverse voltage turn-off time. If the condition is met, the current lead angle is reduced; if the preset condition is not met, the current lead angle is increased.

5. A parallel resonant power factor angle adaptive control system as recited in claim 4, wherein, The determination of whether the lead time corresponding to the lead angle of the current load current is greater than the sum of the commutation time and the reverse voltage turn-off time involves introducing a delay compensation time based on the sum of the commutation time and the reverse voltage turn-off time.

6. A parallel resonant power factor angle adaptive control system as recited in claim 4, wherein, When the conditions are met, the current lead angle is reduced; when the preset conditions are not met, the current lead angle is increased. The adjustment of the lead angle is specifically achieved by changing the phase difference between the current and the voltage by adjusting the triggering time of the SCR.

7. An electronic device comprising a memory, a processor, and a computer program stored on the memory to run on the processor, characterized in that, When the processor executes the program, it implements a parallel resonant power factor angle adaptive control method as described in any one of claims 1-3.

8. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, When the program is executed by the processor, it implements a parallel resonant power factor angle adaptive control method as described in any one of claims 1-3.

Images