Submerged arc furnace frequency conversion power supply control system, method and equipment

Abstract

The invention belongs to the field of power supply control, particularly relates to a variable-frequency power supply control system, method and equipment for a submerged arc furnace, and aims to solve the problems of high power frequency power supply loss, unstable arc, low efficiency and high cost caused by dependence on a high-loss phase-shifting transformer or a high-capacity reactive compensation device in the prior art. The power supply topology is composed of a multi-winding transformer and n variable-frequency power modules, n is a positive integer, and the multi-winding transformer comprises a primary winding and n secondary windings; the primary winding is provided with input ends A, B and C which are connected with a power grid; the output ends ui, vi and wi of the ith secondary winding are connected to the input end of the ith variable-frequency power module, and i is a positive integer and is greater than or equal to 1 and less than or equal to n; the output ends of all the frequency conversion power modules are connected in parallel to form output terminals a and b which are connected with a submerged arc furnace short net. Power grid harmonic waves are eliminated, a reactive power compensation device is omitted, transformer loss is reduced, arc stability is improved, and cost and reliability optimization are considered.

Description

Technical Field

[0001] This invention belongs to the field of power supply control, and specifically relates to a frequency conversion power supply control system, method and equipment for a submerged arc furnace. Background Technology

[0002] Ferroalloys are alloys composed of iron and one or more metals or non-metals. They are indispensable additives in steelmaking, playing a crucial role in adjusting the strength, hardness, corrosion resistance, and wear resistance of steel. Simultaneously, ferroalloys are also a fundamental support and key material in emerging industrial manufacturing sectors, playing a vital role in the national economy. Submerged arc furnaces are the core equipment for producing ferroalloys. Existing large-scale submerged arc furnaces typically use three single-phase on-load tap-changing transformers for power supply. The secondary windings of these three transformers are delta-connected to the short grid of the submerged arc furnace. The supply voltage and current are regulated by the on-load tap-changing transformers, with a power supply frequency of 50Hz. Under power frequency conditions, there are significant eddy current losses and skin effects, rapid consumption of raw materials such as electrodes and coke, unstable electric arcs, low heating efficiency, and high power consumption. Taking a 33MVA ferrosilicon-manganese furnace as an example, a single unit consumes over 250 million kWh of electricity annually. Therefore, submerged arc furnaces are typical high-energy-consuming industrial production equipment.

[0003] Some scholars have proposed reducing the power supply frequency of submerged arc furnaces to improve arc stability and heating efficiency, thereby reducing eddy current losses and raw material consumption rates, and increasing energy utilization efficiency, thus achieving the goal of reducing energy consumption in submerged arc furnace production. However, submerged arc furnaces operate at low voltages and high currents (up to 50kA or more), far exceeding the limits of existing power semiconductor devices, making it extremely difficult to achieve low-frequency power supply for submerged arc furnaces.

[0004] To address the issues of high energy consumption and low heating efficiency in submerged arc furnace (SAF) production, scholars and research institutions both domestically and internationally have conducted extensive research. Utility model patent CN217240605U proposes using a circulating converter to reduce the power supply frequency of the SAF. However, the circulating converter has a low power factor, requiring a bulky and expensive reactive power compensation device. Furthermore, the circulating converter has a large number of thyristors, resulting in high system costs. Invention patents CN109193655A and CN109672172A propose a frequency conversion power supply scheme using a diode uncontrolled rectifier bridge in the front stage and an active inverter in the back stage. This reduces the number of active power semiconductor devices, lowers the cost of the frequency conversion power supply scheme, and improves power supply reliability. However, to meet the grid's harmonic content requirements, this scheme generally requires a multi-winding phase-shifting transformer (with a phase shift angle as low as 15°). High-ratio phase-shifting transformers have extremely low operating efficiency, leading to low overall power supply efficiency for this scheme.

[0005] Based on this, the present invention proposes a frequency conversion power supply control system, method and equipment for a submerged arc furnace. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, namely the large power frequency power loss, unstable electric arc, and the low efficiency and high cost caused by the reliance on high-loss phase-shifting transformers or large-capacity reactive power compensation devices in existing frequency conversion schemes, this invention provides a frequency conversion power supply control system, method, and equipment for submerged arc furnaces.

[0007] In a first aspect, the present invention provides a variable frequency power supply control system for a submerged arc furnace, the system comprising:

[0008] A power supply topology consisting of one multi-winding transformer and n frequency conversion power modules, where n is a positive integer, and the multi-winding transformer includes one primary winding and n secondary windings;

[0009] The primary winding is provided with input terminals A, B, and C connected to the power grid; the output terminals ui, vi, and wi of the i-th secondary winding are connected to the input terminal of the i-th frequency converter power module, where i is a positive integer and 1≤i≤n;

[0010] All the output terminals of the frequency converter power modules are connected in parallel to form output terminals a and b, which are connected to the short network of the electric arc furnace.

[0011] Furthermore, each variable frequency power module consists of a rectifier and an inverter.

[0012] Furthermore, the first j rectifiers in the frequency converter power module are diode uncontrolled rectifier bridges, and the kth rectifier in the frequency converter power module is an active rectifier bridge, where k is a positive integer and j+1≤k≤n;

[0013] All of the inverters mentioned are full-bridge inverters.

[0014] In a second aspect, the present invention provides a variable frequency power supply control method for a submerged arc furnace, used to implement a variable frequency power supply system for a submerged arc furnace, the method comprising:

[0015] The first j frequency converter power module rectifiers are not subject to control;

[0016] The rectifiers of the (j+1)th to (nth)th frequency converter power modules perform the following dual closed-loop control:

[0017] Step S1: Acquire the DC voltage of the rectifier of the k-th frequency converter power module, calculate the difference between the DC voltage and the given DC voltage, and generate an active current reference value i through a proportional-integral controller. dkref And set the reactive current reference value to 0;

[0018] The active current reference value i dkref The difference between the actual active current and the actual active current is used to generate the d-axis reference voltage u via a proportional-integral controller. dkThe difference between the reactive current reference value of 0 and the actual reactive current is used to generate the q-axis reference voltage u via a proportional-integral controller. qk ;

[0019] For u dk and u dk Perform coordinate transformation to generate the first three-phase reference voltage u. ak u bk u ck ;

[0020] Step S2: Collect the three-phase AC current i of the m-th frequency converter power module. am i bm i cm ;

[0021] The collected AC currents of each phase of the first to j-th inverter power modules are summed to calculate the reference current value of the k-th inverter power module. The difference between the reference current value of the k-th inverter power module and the actual current is then used to generate the second three-phase reference voltage u through a proportional-integral controller. ak_HE u bk_HE u ck_HE ;

[0022] Step S3: Calculate the three-phase reference voltages of the rectifier of the k-th frequency converter power module, which are u ak -u ak_HE u bk -u bk_HE u ck -u ck_HE And compared with the carrier wave, the switching signal of the power semiconductor device in the rectifier of the kth inverter in the (j+1)th to (n)th inverter power modules is generated.

[0023] Furthermore, the AC currents of each phase of the collected (1-j)th frequency converter power modules are summed to calculate the reference current value of the kth frequency converter power module. The method is as follows:

[0024]

[0025] Among them, i akref Let i be the reference value for phase a current. bkref i is the reference value for phase b current. ckref This is the reference value for the c-phase current.

[0026] Furthermore, the i-th variable frequency power module inverter generates turn-on and turn-off commands for all inverters based on the reference voltage and carrier comparison issued by the controller of the electric arc furnace variable frequency power supply system.

[0027] Furthermore, all frequency conversion power modules employ unipolar or bipolar sinusoidal pulse width modulation methods on the inverter side.

[0028] Furthermore, the switching signals of the power semiconductor devices in the rectifier of the kth inverter in the (j+1)th to (n)th inverter power modules are generated by sinusoidal pulse width modulation.

[0029] In a third aspect, the present invention provides an electronic device comprising:

[0030] At least one processor; and

[0031] A memory communicatively connected to at least one of the processors; wherein,

[0032] The memory stores instructions that can be executed by the processor to implement a variable frequency power supply control method for an electric arc furnace.

[0033] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer instructions for execution by a computer to implement a variable frequency power supply control method for an electric arc furnace.

[0034] The beneficial effects of this invention are:

[0035] The frequency conversion power supply control system and method for submerged arc furnaces provided by this invention employs a hybrid rectification architecture consisting of a diode uncontrolled rectifier bridge and an active rectifier bridge. While retaining the low-cost advantage of diode rectification, it utilizes the active rectifier bridge to achieve active harmonic compensation, effectively eliminating harmonic currents on the grid side. Therefore, it can achieve unity power factor operation without the need for a large-capacity reactive power compensation device. This design eliminates the reliance on high-loss phase-shifting transformers, using conventional multi-winding transformers to meet power supply requirements, significantly reducing transformer manufacturing difficulty and core losses, and improving power transmission efficiency.

[0036] By employing a modular parallel power unit structure, the ultra-high current required by the electric arc furnace is distributed across multiple frequency converter power modules, overcoming the limitation of insufficient current carrying capacity of single-power semiconductor devices. All inverter units utilize a unified controlled full-bridge topology, coupled with sinusoidal pulse width modulation technology, ensuring phase consistency of the output current across multiple modules and significantly improving arc stability under low-frequency power supply conditions. Ultimately, this approach simultaneously achieves optimized power supply efficiency and a comprehensive improvement in operational reliability while reducing system manufacturing costs and the number of active devices. Attached Figure Description

[0037] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0038] Figure 1 This is a circuit topology diagram of a variable frequency power supply control system for a submerged arc furnace according to the present invention;

[0039] Figure 2 This is a flowchart illustrating a variable frequency power supply control method for a submerged arc furnace according to the present invention.

[0040] Figure 3 This is a schematic diagram of the structure of a computer system used to implement the methods, systems, and devices of this application. Detailed Implementation

[0041] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, the present invention provides a frequency conversion power supply system for a submerged arc furnace, the system comprising:

[0044] A power supply topology consisting of one multi-winding transformer and n frequency conversion power modules, where n is a positive integer, and the multi-winding transformer includes one primary winding and n secondary windings;

[0045] The primary winding is provided with input terminals A, B, and C connected to the power grid; the output terminals ui, vi, and wi of the i-th secondary winding are connected to the input terminal of the i-th frequency converter power module, where i is a positive integer and 1≤i≤n;

[0046] All the output terminals of the frequency converter power modules are connected in parallel to form output terminals a and b, which are connected to the short network of the electric arc furnace.

[0047] In this embodiment, the first j rectifiers in the frequency converter power module are diode uncontrolled rectifier bridges, and the kth rectifier in the frequency converter power module is an active rectifier bridge, where k is a positive integer and j+1≤k≤n;

[0048] All of the inverters mentioned are full-bridge inverters.

[0049] Specifically, the rectifier of the mth inverter power module in the jth inverter power module includes a first diode Dm1, a second diode Dm2, a third diode Dm3, a fourth diode Dm4, a fifth diode Dm5, a sixth diode Dm6, and a DC support capacitor C.

[0050] The anodes of the first diode Dm1, the third diode Dm3, and the fifth diode Dm5 are connected together to form a positive DC bus; the cathodes of the second diode Dm2, the fourth diode Dm4, and the sixth diode Dm6 are connected together to form a negative DC bus.

[0051] The common junction of the first diode Dm1 and the second diode Dm2 is connected to the AC terminal um; the common junction of the third diode Dm3 and the fourth diode Dm4 is connected to the AC terminal vm; the common junction of the fifth diode Dm5 and the sixth diode Dm6 is connected to the AC terminal wm; a DC support capacitor C is connected in parallel between the positive and negative DC buses;

[0052] Where 1≤m≤j, j is a positive even number, and j<n.

[0053] The rectifier of the kth inverter power module among the (j+1)th to nth inverter power modules includes:

[0054] Upper bridge arm devices of the first power semiconductor device Sk1, the third power semiconductor device Sk3, and the fifth power semiconductor device Sk5; lower bridge arm devices of the second power semiconductor device Sk2, the fourth power semiconductor device Sk4, and the sixth power semiconductor device Sk6.

[0055] The first power semiconductor device Sk1 and the second power semiconductor device Sk2 share a common contact and are connected to the AC terminal uk; the third power semiconductor device Sk3 and the fourth power semiconductor device Sk4 share a common contact and are connected to the AC terminal vk; the upper bridge arm devices of the fifth power semiconductor device Sk5 and the sixth power semiconductor device Sk6 share a common contact and are connected to the AC terminal wk.

[0056] A DC support capacitor C is connected in parallel between the midpoint of each bridge arm and the positive and negative DC bus.

[0057] The inverters all have the same structure. Specifically, the inverter of the m-th unit in the j-th module is a full-bridge inverter circuit, comprising:

[0058] The first power semiconductor device Tm1 and the third power semiconductor device Tm3 are connected in series across the positive and negative DC buses; the second power semiconductor device Tm2 and the fourth power semiconductor device Tm4 are connected in series across the positive and negative DC buses; the common connection point of Tm1-Tm2 is connected to the output terminal am through the filter inductor Lm, and the common connection point of Tm3-Tm4 is connected to the output terminal bm through the filter inductor Lm, where m = 1, 2, ..., j;

[0059] The inverter of the kth inverter in the (j+1)th to nth frequency conversion power modules is a full-bridge inverter circuit, comprising:

[0060] The first power semiconductor device Tk1 and the third power semiconductor device Tk3 are connected in series and then connected across the positive and negative DC buses; the second power semiconductor device Tk2 and the fourth power semiconductor device Tk4 are connected in series and then connected across the positive and negative DC buses.

[0061] Tk1-Tk2 are connected to the output terminal ak via a filter inductor Lk; Tk3-Tk4 are connected to the output terminal bk via a filter inductor Lk; where k = j+1, j+2, ..., n.

[0062] like Figure 2 As shown in the second embodiment of the present invention, a variable frequency power supply control method for a submerged arc furnace is proposed to implement a variable frequency power supply system for a submerged arc furnace. The method includes:

[0063] The first j frequency converter power module rectifiers are not subject to control;

[0064] The rectifiers of the (j+1)th to (nth)th frequency converter power modules perform the following dual closed-loop control:

[0065] Step S1: Acquire the DC voltage of the rectifier of the k-th frequency converter power module, calculate the difference between the DC voltage and the given DC voltage, and generate an active current reference value i through a proportional-integral controller. dkref And set the reactive current reference value to 0;

[0066] The active current reference value i dkref The difference between the actual active current and the actual active current is used to generate the d-axis reference voltage u via a proportional-integral controller. dk The difference between the reactive current reference value of 0 and the actual reactive current is used to generate the q-axis reference voltage u via a proportional-integral controller. qk ;

[0067] For u dk and u dk Perform coordinate transformation to generate the first three-phase reference voltage u. ak u bk u ck ;

[0068] Step S2: Collect the three-phase AC current i of the m-th frequency converter power module. am i bm i cm ;

[0069] The collected AC currents of each phase of the first to j-th inverter power modules are summed to calculate the reference current value of the k-th inverter power module. The difference between the reference current value of the k-th inverter power module and the actual current is then used to generate the second three-phase reference voltage u through a proportional-integral controller. ak_HE u bk_HE u ck_HE ;

[0070] Step S3: Calculate the three-phase reference voltages of the rectifier of the k-th frequency converter power module, which are u ak -u ak_HE u bk -u bk_HE uck -u ck_HE The signal is compared with the carrier wave and a switching signal for the power semiconductor device in the rectifier of the kth inverter in the (j+1)th to (n)th inverter power modules is generated by sinusoidal pulse width modulation.

[0071] The variable frequency power supply control method for submerged arc furnaces of the present invention achieves unity power factor operation on the grid side through an active harmonic cancellation mechanism. In specific implementation:

[0072] The diode rectifier bridges of the first j modules operate freely, and the harmonic currents they generate are dynamically compensated by the subsequent k fully controlled rectifier bridges. For each fully controlled rectifier bridge (the kth bridge):

[0073] Inner-loop voltage regulation control adjusts the DC bus voltage in real time: the deviation between the detected DC voltage and the given value is converted into an active current command by a PI controller, and then the basic modulation wave u is generated by a current loop PI controller and dq / abc transformation. ak u bk u ck ;

[0074] The outer loop harmonic compensation synchronously acquires the three-phase current of the preceding j modules, generates a reverse compensation current reference value through summation, and outputs the harmonic compensation voltage u via a PI controller. ak_HE u bk_HE u ck_HE ;

[0075] The modulation signal synthesis subtracts the two sets of voltage signals mentioned above, and the difference is used to generate the drive pulse of the fully controlled device through SPWM modulation. This forces the k-th module to output a compensation current that is opposite in phase to the harmonic current, thereby achieving harmonic neutralization on the grid side.

[0076] This control strategy enables conventional multi-winding transformers to meet harmonic standards without phase-shifting design, while the fully controlled rectifier bridge only needs to handle a portion of the power, significantly reducing system cost and switching losses. All inverter units adopt a unified H-bridge topology and SPWM modulation strategy to ensure amplitude-frequency consistency of parallel outputs and maintain stable low-frequency arc combustion.

[0077] The method for calculating the reference current value of the k-th frequency converter power module is as follows: The AC current of each phase of the collected (1-j)-th frequency converter power modules is summed.

[0078]

[0079] Among them, i akref Let i be the reference value for phase a current. bkref i is the reference value for phase b current. ckref This is the reference value for the c-phase current.

[0080] In this embodiment, all frequency conversion power modules employ unipolar or bipolar sinusoidal pulse width modulation on the inverter side.

[0081] Although the steps in the above embodiments are described in the above order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not need to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple variations are all within the protection scope of this invention.

[0082] An electronic device according to a third embodiment of the present invention includes:

[0083] At least one processor; and

[0084] A memory communicatively connected to at least one of the processors; wherein,

[0085] The memory stores instructions that can be executed by the processor to implement the above-described variable frequency power supply control method for a submerged arc furnace.

[0086] A fourth embodiment of the present invention provides a computer-readable storage medium storing computer instructions, which are executed by the computer to implement the above-described frequency conversion power supply control method for a submerged arc furnace.

[0087] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process and related descriptions of the storage device and processing device described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0088] Those skilled in the art will recognize that the modules and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. The programs corresponding to the software modules and method steps can be placed in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in electronic 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 the invention.

[0089] The following is for reference. Figure 3It shows a schematic diagram of the structure of a computer system for implementing the methods, systems, and devices of this application. Figure 3 The server shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0090] like Figure 3 As shown, the computer system includes a Central Processing Unit (CPU) 301, which can perform various appropriate actions and processes based on programs stored in Read Only Memory (ROM) 302 or programs loaded from storage section 308 into Random Access Memory (RAM) 303. The RAM 303 also stores various programs and data required for system operation. The CPU 301, ROM 302, and RAM 303 are interconnected via a bus 304. An Input / Output (I / O) interface 305 is also connected to the bus 304.

[0091] The following components are connected to I / O interface 305: an input section 306 including a keyboard, mouse, etc.; an output section 307 including a cathode ray tube (CRT), liquid crystal display (LCD), and speakers, etc.; a storage section 308 including a hard disk, etc.; and a communication section 309 including a network interface card such as a LAN (Local Area Network) card and a modem, etc. The communication section 309 performs communication processing via a network such as the Internet. A drive 310 is also connected to I / O interface 305 as needed. Removable media 311, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 310 as needed so that computer programs read from them can be installed into storage section 308 as needed.

[0092] Specifically, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 309, and / or installed from removable medium 311. When the computer program is executed by central processing unit (CPU) 301, it performs the functions defined in the methods of this application. It should be noted that the computer-readable medium described above in this application can be a computer-readable signal medium or a computer-readable storage medium, or any combination of the two. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this application, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on a computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0093] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0094] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0095] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0096] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0097] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A variable frequency power supply system for a submerged arc furnace, characterized in that, The system includes: A power supply topology consisting of one multi-winding transformer and n frequency conversion power modules, where n is a positive integer, and the multi-winding transformer includes one primary winding and n secondary windings; The primary winding is provided with input terminals A, B, and C connected to the power grid; the output terminals ui, vi, and wi of the i-th secondary winding are connected to the input terminal of the i-th frequency converter power module, where i is a positive integer and 1≤i≤n; All the output terminals of the frequency converter power modules are connected in parallel to form output terminals a and b, which are connected to the short network of the electric arc furnace.

2. The frequency conversion power supply system for a submerged arc furnace according to claim 1, characterized in that, Each frequency converter power module consists of a rectifier and an inverter.

3. The frequency conversion power supply system for a submerged arc furnace according to claim 2, characterized in that, The first j rectifiers in the frequency converter power module are diode uncontrolled rectifier bridges, and the kth rectifier in the frequency converter power module is an active rectifier bridge, where k is a positive integer and j+1≤k≤n; All of the inverters mentioned are full-bridge inverters.

4. A variable frequency power supply control method for a submerged arc furnace, used to implement the variable frequency power supply system for a submerged arc furnace as described in any one of claims 1-3, characterized in that, The method includes: The first j frequency converter power module rectifiers are not subject to control; The rectifiers of the (j+1)th to (nth)th frequency converter power modules perform the following dual closed-loop control: Step S1: Acquire the DC voltage of the rectifier of the k-th frequency converter power module, calculate the difference between the DC voltage and the given DC voltage, and generate an active current reference value i through a proportional-integral controller. dkref And set the reactive current reference value to 0; The active current reference value i dkref The difference between the actual active current and the actual active current is used to generate the d-axis reference voltage u via a proportional-integral controller. dk The difference between the reactive current reference value of 0 and the actual reactive current is used to generate the q-axis reference voltage u via a proportional-integral controller. qk ; For u dk and u dk Perform coordinate transformation to generate the first three-phase reference voltage u. ak u bk u ck ; Step S2: Collect the three-phase AC current i of the m-th frequency converter power module. am i bm i cm ; The collected AC currents of each phase of the first to j-th inverter power modules are summed to calculate the reference current value of the k-th inverter power module. The difference between the reference current value of the k-th inverter power module and the actual current is then used to generate the second three-phase reference voltage u through a proportional-integral controller. ak_HE u bk_HE u ck_HE ; Step S3: Calculate the three-phase reference voltages of the rectifier of the k-th frequency converter power module, which are u ak -u ak_HE u bk -u bk_HE u ck -u ck_HE And compared with the carrier wave, the switching signal of the power semiconductor device in the rectifier of the kth inverter in the (j+1)th to (n)th inverter power modules is generated.

5. The frequency conversion power supply control method for a submerged arc furnace according to claim 4, characterized in that, The method for calculating the reference current value of the k-th frequency converter power module is as follows: (The sum of the AC currents of each phase of the collected (1-j)-th frequency converter power modules is as follows:) Among them, i akref Let i be the reference value for phase a current. bkref i is the reference value for phase b current. ckref This is the reference value for the c-phase current.

6. The frequency conversion power supply control method for a submerged arc furnace according to claim 4, characterized in that, The i-th variable frequency power module inverter generates turn-on and turn-off commands for all inverters based on the reference voltage and carrier comparison issued by the controller of the electric arc furnace variable frequency power supply system.

7. The frequency conversion power supply control method for a submerged arc furnace according to claim 6, characterized in that, All frequency converter power modules employ unipolar or bipolar sinusoidal pulse width modulation on the inverter side.

8. The frequency conversion power supply control method for a submerged arc furnace according to claim 4, characterized in that, The switching signals of the power semiconductor devices in the rectifier of the kth inverter in the (j+1)th to (n)th inverter power modules are generated by sinusoidal pulse width modulation.

9. An electronic device, characterized in that, include: At least one processor; as well as A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that can be executed by the processor to implement the variable frequency power supply control method for a submerged arc furnace as described in any one of claims 4-8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that are executed by the computer to implement the variable frequency power supply control method for a submerged arc furnace as described in any one of claims 4-8.

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