Electricity supply system for electric arc furnace based on hybrid current and voltage source converter

Abstract

The application provides a mineral furnace variable frequency power supply system based on a current source and a voltage source converter, and the composition of the mineral furnace variable frequency power supply system comprises one multi-winding transformer and n variable frequency power modules, wherein n is an even positive integer; the multi-winding transformer comprises one primary winding and n secondary windings; the variable frequency power module comprises a rectifier and an inverter; and the multi-winding transformer is connected with the n variable frequency power modules through the n secondary windings. The unit power factor operation of the grid side can be realized, the bulky and expensive reactive compensation device is not needed, the cost of the mineral furnace variable frequency power supply is significantly reduced, the multi-winding phase-shifting transformer is not needed, and the operation efficiency of the mineral furnace variable frequency power supply is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of frequency conversion power supply system technology for electric arc furnaces, and specifically provides a frequency conversion power supply system for electric arc furnaces based on a hybrid current source and voltage source converter. Background Technology

[0002] Submerged arc furnaces are core equipment for producing industrial raw materials such as silicon, ferroalloys, and calcium carbide. Ferroalloys such as ferrosilicon, ferrosilicon, and high-carbon ferrochrome are auxiliary materials for various types of steel smelting and are also fundamental industrial raw materials supporting socio-economic development. Existing high-power 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 furnace electrodes. The power supply voltage is 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 electrodes and coke, unstable electric arcs, low heating efficiency, and high heat loss. Taking a 30MVA ferrosilicon furnace as an example, a single unit consumes over 250 million kWh of electricity annually, making it a typical high-energy-consuming industrial production equipment.

[0003] In response to the national call for energy conservation and carbon reduction in the industrial sector, and to address the problems 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. They have proposed reducing the power supply frequency of SAFs to improve arc stability and heating efficiency, thereby reducing eddy current losses and raw material consumption rates, increasing electrical energy utilization efficiency, and ultimately lowering the energy consumption of SAF production. To address these issues, existing technologies propose adding a frequency converter between the SAF power supply transformer and the power grid to change the SAF power supply frequency.

[0004] Chinese patent CN 217240605 U proposes using a circulating converter to reduce the power supply frequency of an electric arc furnace. However, the circulating converter has a low power factor, requiring a bulky and expensive reactive power compensation device. Chinese patents CN109193655 A and CN 109672172 A propose a back-to-back 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 harmonic content requirements of the grid, this scheme requires a multi-winding phase-shifting transformer. High-ratio phase-shifting transformers have low operating efficiency, resulting in a low overall power supply efficiency for this scheme. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a frequency conversion power supply system for submerged arc furnaces based on a hybrid current source and voltage source converter. This invention's frequency conversion power supply system for submerged arc furnaces, based on a hybrid current source and voltage source converter, can achieve unity power factor operation on the grid side, eliminating the need for bulky and expensive reactive power compensation devices, thus significantly reducing the cost of the frequency conversion power supply for submerged arc furnaces. Furthermore, this invention eliminates the need for multi-winding phase-shifting transformers, significantly improving the operating efficiency of the frequency conversion power supply for submerged arc furnaces.

[0006] The technical objective of this invention is to address the aforementioned problems by providing a frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter. The frequency conversion power supply system for the submerged arc furnace comprises: one multi-winding transformer and n frequency conversion power modules (n being a positive even number).

[0007] The multi-winding transformer includes one primary winding and n secondary windings;

[0008] The variable frequency power module consists of a rectifier and an inverter.

[0009] The multi-winding transformer is connected to n frequency conversion power modules through n secondary windings;

[0010] in,

[0011] The i-th inverter power module rectifier consists of: an input-side filter C f The first power semiconductor device Ti1, the second power semiconductor device Ti2, the third power semiconductor device Ti3, the fourth power semiconductor device Ti4, the fifth power semiconductor device Ti5, the sixth power semiconductor device Ti6, and a DC filter inductor. L dc ;

[0012] The i-th inverter module includes: a DC support capacitor C, a first power semiconductor device Si1, a second power semiconductor device Si2, a third power semiconductor device Si3, a fourth power semiconductor device Si4, and an output filter inductor. L i ;

[0013] i is a positive integer, 1≤i≤n.

[0014] Furthermore, the primary winding of the multi-winding transformer is connected to the power grid via connection terminals A, B, and C;

[0015] Furthermore, the secondary side of the multi-winding transformer is provided with n winding connection terminals, wherein the i-th winding connection terminals ui, vi and wi are connected to the AC side of the i-th frequency converter power module rectifier.

[0016] The DC-side filter inductor of the rectifier of the i-th inverter power module L dc Connected to the DC support capacitor C of the inverter;

[0017] All inverters' AC side is connected via an output filter inductor. L The parallel connection forms output terminals a and b, which are connected to the short grid of the electric arc furnace to supply power to the load.

[0018] Furthermore, the frequency conversion power supply system for the electric arc furnace also includes a controller, the controller structure of which includes a main control board, a control and protection board, a sampling board, a communication board, a fault recording board, and a human-machine interaction system;

[0019] The variable frequency power supply system for the electric arc furnace uses the line voltage U of the j-th winding on the secondary side of a multi-winding transformer. uwj The zero-crossing point is the phase start reference point. The commutation angle θ issued by the controller allocates the on / off state of the rectifier of the frequency converter power module, where 1≤j≤n / 2 and 0°≤θ≤180°.

[0020] Furthermore, the rectifier's on / off state control process is as follows:

[0021] (1) When the line voltage U uwj When the phase is θ~θ+60°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned on.

[0022] (2) When the line voltage U uwj When the phase is θ+60°~θ+120°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0023] (3) When the line voltage U uwj When the phase is θ+120°~θ+180°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0024] (4) When the line voltage U uwjWhen the phase is θ+180°~θ+240°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0025] (5) When the line voltage U uwj When the phase is θ+240°~θ+300°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned off.

[0026] (6) When the line voltage U uwj When the phase is θ+300°~θ+360°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned on.

[0027] Furthermore, taking the line voltage U of the kth winding on the secondary side of a multi-winding transformer as an example... uwk The zero-crossing point is the phase start reference point. The commutation angle -θ issued by the controller is used to allocate the rectifier conduction and cutoff states of the frequency converter power module, where n / 2+1≤k≤n.

[0028] Furthermore, the rectifier's on / off state control process is as follows:

[0029] (1) When the line voltage U uwk When the phase is θ to θ+60°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned on.

[0030] (2) When the line voltage U uwk When the phase is θ+60°~θ+120°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0031] (3) When the line voltage U uwkWhen the phase is θ+120°~θ+180°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0032] (4) When the line voltage U uwk When the phase is θ+180°~θ+240°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0033] (5) When the line voltage U uwk When the phase is θ+240°~θ+300°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned off.

[0034] (6) When the line voltage U uwk When the phase is θ+300°~θ+360°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned on.

[0035] Furthermore, the inverter of the i-th frequency conversion power module of the electric arc furnace frequency conversion power supply system generates turn-on and turn-off commands for the first power semiconductor device Si1, the second power semiconductor device Si2, the third power semiconductor device Si3, and the fourth power semiconductor device Si4 based on the reference voltage and carrier wave issued by the controller, using a unipolar or bipolar modulation method.

[0036] Furthermore, the first power semiconductor device Ti1, the second power semiconductor device Ti2, the third power semiconductor device Ti3, the fourth power semiconductor device Ti4, the fifth power semiconductor device Ti5, and the sixth power semiconductor device Ti6 each include an NPN transistor and a diode, wherein the negative terminal of the diode is connected to the emitter of the transistor.

[0037] Furthermore, the first power semiconductor device Si1, the second power semiconductor device Si2, the third power semiconductor device Si3, and the fourth power semiconductor device Si4 each include an NPN transistor and a diode, wherein the positive and negative terminals of the diode are connected to the emitter and collector of the transistor, respectively.

[0038] Compared with existing technologies, the frequency conversion power supply system for submerged arc furnaces based on a hybrid current source and voltage source converter of the present invention has the following outstanding advantages:

[0039] The present invention provides a frequency conversion power supply system for ferroelectric furnaces based on a hybrid current source and voltage source converter, which can achieve unity power factor operation on the grid side. It eliminates the need for bulky and expensive reactive power compensation devices, significantly reducing the cost of frequency conversion power supply for ferroelectric furnaces. The present invention also eliminates the need for multi-winding phase-shifting transformers, significantly improving the operating efficiency of frequency conversion power supply for ferroelectric furnaces. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the frequency conversion power supply topology for a submerged arc furnace based on a hybrid current source and voltage source converter according to the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0042] like Figure 1 As shown, a variable frequency power supply system for a submerged arc furnace (SAF) based on a hybrid current source and voltage source converter is disclosed. The SAF system comprises one multi-winding transformer and n variable frequency power modules (n being a positive even number). The multi-winding transformer includes one primary winding and n secondary windings; each variable frequency power module consists of a rectifier and an inverter.

[0043] The i-th (i is a positive integer, 1≤i≤n) frequency converter power module rectifier includes an input-side filter C f The first power semiconductor device Ti1, the second power semiconductor device Ti2, the third power semiconductor device Ti3, the fourth power semiconductor device Ti4, the fifth power semiconductor device Ti5, the sixth power semiconductor device Ti6, and a DC filter inductor. L dc ;

[0044] The first power semiconductor device Ti1 and the fourth power semiconductor device Ti4 are connected in series; the second power semiconductor device Ti2 and the fifth power semiconductor device Ti5 are connected in series; the third power semiconductor device Ti3 and the sixth power semiconductor device Ti6 are connected in series; and the series-connected power semiconductor devices are then connected in parallel.

[0045] The i-th inverter module includes a DC support capacitor C, a first power semiconductor device Si1, a second power semiconductor device Si2, a third power semiconductor device Si3, a fourth power semiconductor device Si4, and an output filter inductor. L i .

[0046] The first power semiconductor device Si1 and the third power semiconductor device Si3 are connected in series, the second power semiconductor device Si2 and the fourth power semiconductor device Si4 are connected in series, and the series-connected power semiconductor devices are then connected in parallel.

[0047] The DC-side filter inductor of the i-th inverter power module rectifier L dc Connect to the DC support capacitor C of the inverter in the variable frequency power module;

[0048] All inverters on the AC side of the variable frequency power module are connected to the output filter inductor. L The parallel connection forms output terminals a and b, which are connected to the short grid of the electric arc furnace to supply power to the load.

[0049] The aforementioned frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter connects the power grid to terminals A, B, and C on the primary side of a multi-winding transformer; and terminals ui, vi, and wi on the secondary side of the multi-winding transformer are connected to the AC side of the rectifier of the i-th frequency conversion power module.

[0050] The aforementioned frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter uses the line voltage U of the j-th (1≤j≤n / 2) winding on the secondary side of a multi-winding transformer. uwj The zero-crossing point is used as the phase starting reference point. The on / off state of the rectifier of the frequency converter power module is allocated according to the commutation angle θ (0°≤θ≤180°) issued by the controller. The specific allocation rules are as follows:

[0051] (1) When the line voltage U uwj When the phase is θ~θ+60°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned on.

[0052] (2) When the line voltage U uwj When the phase is θ+60°~θ+120°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0053] (3) When the line voltage U uwj When the phase is θ+120°~θ+180°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0054] (4) When the line voltage U uwj When the phase is θ+180°~θ+240°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off.

[0055] (5) When the line voltage U uwj When the phase is θ+240°~θ+300°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned off.

[0056] (6) When the line voltage U uwj When the phase is θ+300°~θ+360°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned on.

[0057] The aforementioned frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter uses the line voltage U of the kth (n / 2+1≤k≤n) winding on the secondary side of a multi-winding transformer. uwk The zero-crossing point is the initial phase reference point. The on / off states of the inverter power module rectifier are allocated based on the commutation angle -θ issued by the controller, according to the following rules:

[0058] (1) When the line voltage U uwk When the phase is θ to θ+60°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned on.

[0059] (2) When the line voltage U uwk When the phase is θ+60°~θ+120°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0060] (3) When the line voltage U uwk When the phase is θ+120°~θ+180°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0061] (4) When the line voltage U uwk When the phase is θ+180°~θ+240°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off.

[0062] (5) When the line voltage U uwk When the phase is θ+240°~θ+300°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned off.

[0063] (6) When the line voltage U uwk When the phase is θ+300°~θ+360°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned on.

[0064] In the aforementioned frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter, the i-th frequency conversion power module inverter generates on / off commands for the first power semiconductor device Si1, the second power semiconductor device Si2, the third power semiconductor device Si3, and the fourth power semiconductor device Si4 according to the reference voltage and carrier wave issued by the controller.

[0065] The deployment of the frequency conversion power supply system for the submerged arc furnace based on a hybrid current source and voltage source converter is as follows: One multi-winding transformer is independently installed in the power distribution room; n frequency conversion power modules (n being a positive even number) are installed in parallel in one or more enclosures as frequency conversion units, independently installed in the power distribution room; the control system is installed in one or more control cabinets, independently installed in the power distribution room or operating room. The multi-winding transformer is connected to the frequency conversion unit via cables or copper busbars, and the frequency conversion unit is connected to the short-network terminal side of the submerged arc furnace via cables. The controller is connected to the frequency conversion unit via optical fiber.

[0066] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter, characterized in that, The variable frequency power supply system for the electric arc furnace consists of: one multi-winding transformer and n variable frequency power modules, where n is a positive even number; The multi-winding transformer includes one primary winding and n secondary windings; The variable frequency power module consists of a rectifier and an inverter. The multi-winding transformer is connected to n frequency conversion power modules through n secondary windings; in, The i-th inverter power module rectifier consists of: an input-side filter C f The first power semiconductor device Ti1, the second power semiconductor device Ti2, the third power semiconductor device Ti3, the fourth power semiconductor device Ti4, the fifth power semiconductor device Ti5, the sixth power semiconductor device Ti6, and the DC filter inductor L dc ; The i-th inverter module includes: a DC support capacitor C, a first power semiconductor device Si1, a second power semiconductor device Si2, a third power semiconductor device Si3, a fourth power semiconductor device Si4, and an output filter inductor L. i ; i is a positive integer, 1≤i≤n; The primary winding of the multi-winding transformer is connected to the power grid through terminals A, B, and C. The secondary side of the multi-winding transformer is provided with n winding connection terminals, wherein the i-th winding connection terminals ui, vi and wi are connected to the AC side of the i-th frequency converter power module rectifier. The DC-side filter inductor L of the rectifier of the i-th inverter power module dc Connected to the DC support capacitor C of the inverter; The AC sides of all inverters are connected in parallel through the output filter inductor L to form output terminals a and b, which are connected to the short grid of the electric arc furnace to supply power to the load. The frequency conversion power supply system for the electric arc furnace also includes a controller, the controller structure of which includes a main control board, a control and protection board, a sampling board, a communication board, a fault recording board, and a human-machine interaction system; The variable frequency power supply system for the electric arc furnace uses the line voltage U of the j-th winding on the secondary side of a multi-winding transformer. uwj The zero-crossing point is the phase start reference point. The commutation angle θ issued by the controller is used to allocate the rectifier conduction and cutoff states of the frequency converter power module, where 1≤j≤n / 2 and 0°≤θ≤180°. The rectifier on / off state control process is as follows: (1) When the line voltage U uwj When the phase is θ~θ+60°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned on. (2) When the line voltage U uwj When the phase is θ+60°~θ+120°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned on, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off. (3) When the line voltage U uwj When the phase is θ+120°~θ+180°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned on, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off. (4) When the line voltage U uwj When the phase is θ+180°~θ+240°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned on, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned off, and the sixth power semiconductor device Tj6 is turned off. (5) When the line voltage U uwj When the phase is θ+240°~θ+300°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned on, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned off. (6) When the line voltage U uwj When the phase is θ+300°~θ+360°, the first power semiconductor device Tj1 of the j-th inverter power module rectifier is turned off, the second power semiconductor device Tj2 is turned off, the third power semiconductor device Tj3 is turned off, the fourth power semiconductor device Tj4 is turned off, the fifth power semiconductor device Tj5 is turned on, and the sixth power semiconductor device Tj6 is turned on.

2. The frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter as described in claim 1, characterized in that, The line voltage U of the kth winding on the secondary side of a multi-winding transformer uwk The zero-crossing point is the phase start reference point. The commutation angle -θ issued by the controller is used to allocate the rectifier conduction and cutoff states of the frequency converter power module, where n / 2+1≤k≤n.

3. The frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter as described in claim 2, characterized in that, The rectifier on / off state control process is as follows: (1) When the line voltage U uwk When the phase is θ to θ+60°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned on. (2) When the line voltage U uwk When the phase is θ+60°~θ+120°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned on, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off. (3) When the line voltage U uwk When the phase is θ+120°~θ+180°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned on, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off. (4) When the line voltage U uwk When the phase is θ+180°~θ+240°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned on, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned off, and the sixth power semiconductor device Tk6 is turned off. (5) When the line voltage U uwk When the phase is θ+240°~θ+300°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned on, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned off. (6) When the line voltage U uwk When the phase is θ+300°~θ+360°, the first power semiconductor device Tk1 of the k-th inverter power module rectifier is turned off, the second power semiconductor device Tk2 is turned off, the third power semiconductor device Tk3 is turned off, the fourth power semiconductor device Tk4 is turned off, the fifth power semiconductor device Tk5 is turned on, and the sixth power semiconductor device Tk6 is turned on.

4. The frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter as described in claim 2 or 3, characterized in that, The inverter of the i-th frequency conversion power module in the electric arc furnace frequency conversion power supply system generates turn-on and turn-off commands for the first power semiconductor device Si1, the second power semiconductor device Si2, the third power semiconductor device Si3, and the fourth power semiconductor device Si4 based on the reference voltage and carrier wave issued by the controller.

5. The frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter according to claim 4, characterized in that, The first power semiconductor device Ti1, the second power semiconductor device Ti2, the third power semiconductor device Ti3, the fourth power semiconductor device Ti4, the fifth power semiconductor device Ti5, and the sixth power semiconductor device Ti6 each include an NPN transistor and a diode, wherein the negative terminal of the diode is connected to the emitter of the transistor.

6. The frequency conversion power supply system for a submerged arc furnace based on a hybrid current source and voltage source converter according to claim 4, characterized in that, The first power semiconductor device Si1, the second power semiconductor device Si2, the third power semiconductor device Si3, and the fourth power semiconductor device Si4 each include an NPN transistor and a diode, wherein the positive and negative terminals of the diode are connected to the emitter and collector of the transistor, respectively.

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