CN104092379A - A Welding and Cutting Network System Based on DC Bus Structure - Google Patents

Abstract

The invention discloses a welding and cutting network system based on a direct-current bus structure. The welding and cutting network system comprises a power grid, an EMI filter, a first filtering circuit, a first rectifying circuit, a direct-current bus and an inverter power source circuit. The direct-current bus provides a direct-current power source for a plurality of welding and cutting power sources, a plurality of welding power sources and a plurality of cutting power sources. A plurality of inversion type welding and cutting power sources are connected to the same direct-current bus to form the welding and cutting network system based on the direct-current bus structure, the welding and cutting power sources only need to complete direct current-direct current conversion, the power density of the welding and cutting power sources is improved, centralized management of current harmonics is achieved, the work reliability of the whole welding and cutting system is greatly improved, and the mutual influence between devices is reduced. The influence of non-linear load current distortion on the power grid is effectively avoided, the influence of third harmonic currents on the power grid can be insulated, and the influence of high-frequency interference signals on other devices on the power grid is lowered. When accidents happen to a welding and cutting network, faults can be cut off fast, and the accidents of the welding and cutting power grid are prevented from being enlarged.

Description

A Welding and Cutting Network System Based on DC Bus Structure

technical field

The invention belongs to the technical field of welding and cutting power supplies, and more specifically relates to a welding and cutting network system based on a DC bus structure.

Background technique

Arc welding power supply and plasma cutting power supply are the main components of welding and cutting equipment. The development of welding and cutting equipment industry is directly related to aerospace, aviation, metallurgy, energy, machinery manufacturing, shipbuilding, automobile, petrochemical, electric power and other industries The development of the country plays a key role in the development of the country's industry. In industrial applications, arc welding power supplies and plasma cutting power supplies have higher requirements for their own dynamic response characteristics and reliability than general power supplies. The key issue is to realize high power density, high stability, high efficiency and low harmonic pollution of welding and cutting power supply.

At present, most of the arc welding power supply and plasma cutting power supply at home and abroad are traditional three-phase AC input, first pass through a three-phase rectifier circuit, after rectification and conversion, pass through an inverter circuit, and finally rectify and output DC power. For example, the YD series DC arc welding power source produced by Tangshan Matsushita Industrial Machinery Co., Ltd. uses a diode uncontrolled rectification topology for the rectifier circuit, and a full-bridge IGBT topology for the inverter circuit. The machine with a power of 16.7kW weighs 50kg and has an efficiency of only 85%. %, when this circuit is directly connected to the power grid, there is current distortion, high frequency interference, and low power factor. Another example is the power max series machine-use plasma cutting power supply produced by Haibao Company of the United States. The input end of the power supply is connected with an electromagnetic interference (EMI) filter. The rectification circuit is an uncontrolled rectification circuit topology. When this power supply is directly connected to the grid, it can suppress high-frequency interference, but there are still problems of current distortion and low power factor. Welding and cutting power supplies at home and abroad generally have the problems of low power supply efficiency, large volume, heavy weight and current harmonic pollution. However, the welding and cutting network system based on the DC bus structure has not been proposed yet.

Contents of the invention

Aiming at the defects of the prior art, the purpose of the present invention is to provide a welding and cutting network system based on the DC bus structure, which solves the problems of low power density, current harmonic pollution and low reliability of the existing welding and cutting power supply.

The invention provides a welding and cutting network system based on a DC bus structure, including a power grid, an EMI filter, a first filter circuit, a first rectifier circuit, a DC bus and an inverter power supply circuit; the input end of the EMI filter is connected to the The output end of the power grid is connected, and the EMI filter is used to suppress high-frequency interference signals in the circuit to improve the electromagnetic compatibility performance of the system; the input end of the first filter circuit is connected to the output end of the EMI filter, The first filter circuit is used to further filter harmonics of the signal after filtering out high-frequency interference; the input terminal of the first rectifier circuit is connected to the output terminal of the first filter circuit, and the first rectifier circuit It is used to convert the three-phase AC voltage source after harmonic filtering into a DC voltage source and provide it to the DC bus; the input end of the DC bus is connected to the output end of the first rectifier circuit, and the DC bus The output end of the inverter is connected to the inverter power circuit; the DC bus is used to provide DC power for the inverter power circuit.

Wherein, the first filter circuit includes a three-phase input inductor, a first harmonic filter, a second harmonic filter, and a third harmonic filter; one end of the three-phase input inductor is connected to the output of the EMI filter, The other end of the three-phase input inductance is used as the output end of the first filter circuit; the first harmonic filter, the second harmonic filter and the third harmonic filter are sequentially connected in parallel to the first filter circuit on the three-phase output line.

Wherein, the circuit structures of the first harmonic filter, the second harmonic filter and the third harmonic filter are the same; the first harmonic filter includes a first inductor, a second inductor, a third inductor, The first capacitance, the second capacitance and the third capacitance; one end of the first inductance, one end of the second inductance and one end of the third inductance are sequentially connected to the three-phase output line of the first filter circuit respectively On; one end of the third capacitor is connected to the other end of the first inductance, and the other end of the third capacitor is connected to the other end of the third inductance; the first capacitor and the second capacitor connected in parallel with the third capacitor in series, and the parallel connection end of the first capacitor and the second capacitor is connected with the other end of the second inductor.

Wherein, the inverter power supply circuit is a welding and cutting power supply for converting the DC power provided by the DC bus into a voltage and current required for welding or cutting, and for converting the DC power provided by the DC bus into A welding power supply with the voltage and current required by the welding condition or/and a cutting power supply for converting the DC power provided by the DC bus into a voltage and current required by the cutting condition.

Wherein, the welding and cutting power supply includes an inverter circuit, a resonant circuit, a second rectifier circuit and a second filter circuit connected in sequence.

Wherein, the inverter circuit converts the DC voltage of the power supply into a periodically changing positive and negative half cycle symmetrical square wave voltage by controlling the switching state of the switching tube; it includes the first switching tube Q ₁ , the second switching tube Q ₂ , the second switching tube Three switch tubes Q ₃ , fourth switch tube Q ₄ , first buffer capacitor C ₁ connected in parallel with the first switch tube Q ₁ , second buffer capacitor C ₂ connected in parallel with the second switch tube Q ₂ , the third buffer capacitor C ₃ connected in parallel with the third switch tube Q ₃ , the fourth buffer capacitor C ₄ connected in parallel with the fourth switch tube Q ₄ , and the reverse direction of the first switch tube Q ₁ The first diode D ₁ connected in parallel, the second diode D ₂ connected in antiparallel with the second switch transistor Q ₂ , the third diode D connected in reverse parallel with the third switch transistor Q _{3 3} and the fourth diode _D4 connected in antiparallel with the fourth switch tube _Q4 ; the input terminal of the first switch tube _Q1 and the input terminal of the second switch tube _Q2 are connected to the positive pole of the power supply , the output terminal of the fourth switching tube _Q4 and the output terminal of the third switching tube _Q3 are connected to the negative pole of the power supply; the output terminal of the first switching tube _Q1 is connected to the third switching tube _Q3 The input terminal of the fourth switch tube _Q4 is connected to the output terminal of the second switch tube _Q2 .

Wherein, the first switching tube Q ₁ , the second switching tube Q ₂ , the third switching tube Q ₃ and the fourth switching tube Q ₄ are the same, and are IGBT, SiC, GaAs with higher switching frequency semiconductor power devices.

Wherein, the resonant circuit includes a resonant inductance L _r , a resonant capacitor C _r and a high-frequency isolation transformer T; one end of the resonant capacitor C _r is connected to the connection end of the first switching tube _Q1 and the third switching tube _Q3 , One end of the resonant inductance L _r is connected to the other end of the resonant capacitor C _r , the other end of the resonant inductance L _r is connected to one end of the primary coil of the high-frequency isolation transformer T, and the other end of the primary coil is connected to the second switching tube Q ₂ and the connection end of the fourth switching tube _Q4 ; under the excitation of the square wave voltage, the resonant inductance L _r , the resonant capacitor C _r and the equivalent excitation inductance of the primary side of the high-frequency isolation transformer generate approximately sinusoidal The high-frequency resonant current is transmitted to the secondary side through the primary side of the high-frequency isolation transformer.

Wherein, the second rectifier circuit converts the high-frequency resonance current of the secondary side of the high-frequency isolation transformer into a direct current; the second rectifier circuit includes a diode _D5 and a diode _D6 ; the diode _D5 and the diode _D6 After the cathode is connected in parallel, it is used as the output end of the second rectifier circuit. The anode of the diode _D5 is connected to the first end of the secondary coil of the high-frequency isolation transformer T, and the anode of the diode _D6 is connected to the first end of the secondary coil of the high-frequency isolation transformer T. The three terminals are connected, and the second terminal of the secondary coil of the high-frequency isolation transformer T is grounded.

Wherein, the second filter circuit provides a stable DC power supply for the load by suppressing the fluctuation of the output DC current of the second rectifier circuit; the second filter circuit includes a DC filter inductor L ₀ and a DC filter capacitor C ₀ ; the One end of the DC filter inductor _L0 is used as the input end of the second filter circuit, the other end of the DC filter inductor _L0 is grounded through the DC filter capacitor _C0 , and the other end of the DC filter inductor _L0 is also As the output terminal of the second filter circuit.

The present invention utilizes this common DC busbar structure to greatly improve the working reliability of the entire welding and cutting system and reduce the mutual influence between devices; the DC busbar directly provides the DC voltage source of the welding and cutting power supply, which reduces the The rectification conversion circuit not only improves the power density of the welding and cutting power supply, but also improves the efficiency of the welding and cutting power supply; under the half-load condition of the entire DC welding and cutting network system, the total harmonic distortion (Total Harmonic Distortion, THD) of the input current ) is lower than 3%, which effectively prevents the impact of nonlinear load current distortion on the grid, ensures the power quality of the grid, and reduces the impact of high-frequency interference signals on other equipment on the grid.

Description of drawings

Fig. 1 is the schematic structural diagram of the welding and cutting network system based on the DC bus structure provided by the embodiment of the present invention;

2 is a schematic diagram of a filter circuit in a welding and cutting network system based on a DC bus structure provided by an embodiment of the present invention;

3 is a schematic diagram of a three-phase rectifier circuit in a welding and cutting network system based on a DC bus structure provided by an embodiment of the present invention;

Fig. 4 is a schematic diagram of the inverter power supply in the welding and cutting network system based on the DC bus structure provided by the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention provides a welding and cutting network system based on a DC bus structure, including an input three-phase power supply, an EMI (electromagnetic interference) filter, a filter circuit, a three-phase rectifier circuit, a DC bus, and an inverter power supply circuit. The input end of the EMI filter is connected to the output end of the three-phase power supply provided by the grid, and the EMI filter is used to suppress the high-frequency interference signal in the circuit, effectively improving the electromagnetic compatibility performance of the system; the input end of the filter circuit is connected to the EMI filter The output end of the rectifier is connected, and the filter circuit is used to filter the three-phase input current of the rectifier circuit, and filter out the low-frequency harmonic current; the input end of the three-phase rectifier circuit is connected to the output end of the filter circuit, and the three-phase The rectifier circuit is used to convert the three-phase periodic AC voltage into a DC voltage; the output terminal of the three-phase rectifier circuit is connected to the input terminal of the DC bus, and the DC bus provides the DC voltage source for the inverter power circuit; the inverter The variable power supply circuit includes welding and cutting power supply, welding power supply and cutting power supply; the input end of the welding and cutting power supply is connected to the DC bus bar, the input end of the welding power supply is connected to the DC bus bar, the input end of the cutting power supply is also connected to the DC bus bar, and the DC bus bar provides The multiple welding and cutting power supplies, the multiple welding power supplies and the multiple cutting power supplies are DC power supplies.

Wherein, the input end of the EMI filter is connected to the output end of the grid, and the output end of the EMI filter is connected to the input end of the filter circuit. The EMI filter is used to suppress high-frequency interference signals in the circuit and effectively improve the electromagnetic compatibility performance of the system.

Wherein, the input end of the filter circuit is connected to the output end of the EMI filter, and the output end of the filter circuit is connected to the input of the rectification circuit. The filtering circuit is used for filtering the input current of the rectifying circuit, and filtering out the low-frequency harmonic current therein.

Wherein, the input end of the rectification circuit is connected with the output end of the filter circuit, and the output end of the rectification circuit is connected with the input end of the DC bus. The rectifier circuit is used to convert the three-phase AC voltage source into a DC voltage source, and the converted DC voltage source is provided to the DC bus.

Wherein, the input terminals of multiple welding and cutting power supplies are connected to the output terminals of the DC bus, the input terminals of multiple welding power supplies are connected to the output terminals of the DC bus, and the input terminals of multiple cutting power supplies are connected to the output terminals of the DC bus; The welding and cutting power supply is used to convert the DC bus voltage into the voltage and current required for welding or cutting conditions, so as to realize the welding or cutting of the workpiece; the welding power supply is used to convert the DC bus voltage into the voltage and current required for welding conditions, Realize the welding of the workpiece; the cutting power supply is used to convert the voltage provided by the DC bus into a voltage and current suitable for cutting conditions to realize the cutting of the workpiece.

Compared with the prior art, the embodiment of the present invention utilizes this common DC bus structure, which greatly improves the working reliability of the entire welding and cutting system and reduces the mutual influence between devices; the DC bus directly provides the DC voltage of the welding and cutting power supply source, so that the welding and cutting power supply itself reduces the rectification conversion circuit, which not only improves the power density of the welding and cutting power supply, but also improves the efficiency of the welding and cutting power supply; The wave distortion rate (Total Harmonic Distortion, THD) is lower than 3%, which effectively prevents the impact of nonlinear load current distortion on the grid, ensures the power quality of the grid, and reduces the impact of high-frequency interference signals on other equipment on the grid.

A welding and cutting network system based on the DC bus structure proposed by the present invention can solve the existing problems of low power density and current harmonic pollution of welding and cutting power sources, as well as the traditional low reliability problems. Under the load condition, its input current THD is lower than 3%, which is suitable for the application field of high-power welding and cutting power supply.

Figure 1 shows the structure of the welding and cutting network system based on the DC bus structure provided by the embodiment of the present invention. For the convenience of description, only the parts related to the embodiment of the present invention are shown, and the details are as follows:

The welding and cutting network system based on the DC bus structure includes: a three-phase power supply 1 provided by the grid, an EMI filter 2, a first filter circuit 3, a first rectifier circuit 4, a DC bus 5, and an inverter power circuit 6; among them, the EMI filter The input terminal of the device 2 is connected to the output terminal of the three-phase power supply 1 provided by the grid, the input terminal of the first filter circuit 3 is connected to the output terminal of the EMI filter 2, and the input terminal of the three-phase first rectifier circuit 4 is connected to the first filter circuit 3, the output end of the three-phase first rectifier circuit 4 is connected to the input end of the DC bus 5, the inverter power supply circuit 6 includes a welding and cutting power supply 61, a welding power supply 62 and a cutting power supply 63, and the input of the welding and cutting power supply 61 The terminal is connected with the DC bus 5, the input end of the welding power supply 62 is connected with the DC bus 5, the input end of the cutting power supply 63 is also connected with the DC bus 5, and the DC bus 5 provides the DC power supply for the inverter power circuit 6; the EMI filter 2 is used The high-frequency interference signal in the suppression circuit can effectively improve the electromagnetic compatibility performance of the system; the first filter circuit 3 is used to filter the three-phase input current of the first rectifier circuit 4, and filter out the harmonics; the first The rectifier circuit 4 is used to convert the three-phase AC voltage into a DC voltage, which is provided to the DC bus 5; the DC bus 5 is used as a common DC power supply, and is provided to the welding and cutting power supply 61, the welding power supply 62 and the cutting power supply 63 DC power supply The welding and cutting power supply 61 is used to convert the voltage of the DC bus 5 into the voltage and current required for welding or cutting conditions, so as to realize the welding or cutting of the workpiece; the welding power supply 62 is used to convert the voltage of the DC bus 5 It is converted into the voltage and current required by the welding condition to realize the welding of the workpiece; the cutting power supply 63 is used to convert the voltage provided by the DC bus 5 into a voltage and current suitable for the cutting condition to realize the cutting of the workpiece.

The present invention provides a welding and cutting network system based on a DC bus structure, which belongs to an application in power automation equipment and power electronic conversion, and aims to solve the problems of low power density and current harmonic pollution of welding and cutting power supplies , Under the half-load condition of the welding and cutting network system, its input current THD is lower than 3%, and it can effectively reduce the impact of high-frequency interference signals on other equipment on the power grid.

2 is a schematic diagram of a filter circuit in a welding and cutting network system based on a DC bus structure provided by an embodiment of the present invention. As shown in the figure, the first filter circuit 3 is composed of a three-phase input inductor 31, a first harmonic filter 32 The second harmonic filter 33 and the third harmonic filter 34 are composed. One end of the three-phase input inductance 31 is connected to the output of the EMI filter, the other end of the three-phase input inductance 31 is the output end of the first filter circuit 3, the first harmonic filter 32, the second harmonic filter 33 and the second harmonic filter The three harmonic filters 34 are all connected in parallel on the three-phase output lines of the first filter circuit 3, and the three-phase input inductance 31 includes three groups of filter inductors, which are respectively connected in series in the three-phase circuit, and the first harmonic filter 32 includes The three inductors of the three-phase input and the three capacitors of the delta connection structure, the circuit structures of the first harmonic filter 32 , the second harmonic filter 33 and the third harmonic filter 34 are the same. The output terminal of the first filter circuit 3 is connected to the input of the first rectification circuit 4 . The first filtering circuit 3 is used for filtering the three-phase input AC current of the first rectifying circuit 4 to filter out harmonics therein. The filter circuit used in this embodiment is not the only filter circuit that can be used, and it is not intended to limit the present invention. All filter circuits that can achieve the same filter effect are within the scope of protection, such as active filter circuit structures.

In the embodiment of the present invention, the three-phase rectification adopts a 12-pulse uncontrolled rectification circuit, the schematic diagram of which is shown in Fig. rectifier bridge 42 , first balance reactor 43 and second balance reactor 44 . The input end of the three-phase autotransformer is connected with the output end of the first filter circuit 3, the three-phase autotransformer includes two sets of three-phase output voltages, one set of three-phase voltage sources is connected with the input end of the first rectifier bridge 41, and the other A group of three-phase voltage sources is connected to the input terminal of the second rectifier bridge 42, and the output terminals of the first rectifier bridge 41 and the second rectifier bridge 42 are connected in parallel. Wherein, the output positive pole of the first rectifier bridge 41 and the output positive pole of the second rectifier bridge 42 are connected to the two input ends of the first balance reactor 43, the output negative pole of the first rectifier bridge 41 and the output negative pole of the second rectifier bridge 42 It is connected to the two input terminals of the second balance reactor 44, and the first balance reactor 43 and the second balance reactor 44 provide DC voltage to the input terminals of the DC bus. In particular, the three-phase cross-connected autotransformer is used to convert the input three-phase voltage into two sets of three-phase output voltages, and the phase difference between the same phase voltages of the two sets of three-phase output voltages is 30 degrees, that is The phase difference between the a1 _- phase voltage of the first group of three-phase output voltage and the _a2- phase voltage of the second group of three-phase output voltage is 30 degrees, and the two sets of three-phase voltages output by the three-phase autotransformer are respectively input to the first rectifier bridge 41 and the second bridge rectifier 42. Wherein, both the first rectifier bridge 41 and the second rectifier bridge 42 are used to convert the three-phase AC voltage into a DC voltage, and the DC voltage output by the first rectifier bridge 41 and the second rectifier bridge 42 in parallel is input to the DC bus. The rectification circuit used in this embodiment is not the only rectification converter that can be used, and it is not intended to limit the present invention. All circuit structures that can achieve the same rectification conversion function are within the scope of protection, such as twelve-pulse controllable Rectifier circuit, 24-pulse uncontrolled rectifier circuit, etc.

In the embodiment of the present invention, as shown in Figure 1, the input end of the DC bus 5 is connected to the output end of the first rectifier circuit 4, and the output end of the DC bus 5 is connected to the welding and cutting power supply 61, the welding power supply 62 and the cutting power supply 63 respectively. input connection. The DC bus 5 provides a common DC power supply to the welding and cutting power supply 61, welding power supply 62 and cutting power supply 63 connected to the DC bus 5. The number of welding and cutting equipment connected to the DC bus 5 depends on the output of the DC welding and cutting network system. The power level is determined by the power level. The number of connected welding and cutting equipment shown in this embodiment is only a representative description, not the number of welding and cutting equipment in the actual welding and cutting network system. In the embodiment of the present invention, a welding and cutting network system based on the structure of the DC bus is formed by connecting multiple inverter welding and cutting power sources on the same DC bus. The power density of the cutting power supply also realizes the centralized management of current harmonics, which greatly improves the reliability of the entire welding and cutting system and reduces the mutual influence between equipment; effectively prevents the influence of nonlinear load current distortion on the power grid, especially It can isolate the influence of the 3rd harmonic current on the power grid and ensure the power quality of the power grid. Under the half-load condition of the welding and cutting network system, the total harmonic distortion rate THD of the input current is lower than 3%; it reduces the impact of high-frequency interference signals on the power grid. The impact of other equipment on the power grid; when an accident occurs in the welding and cutting network, the fault can be quickly removed to prevent the expansion of the accident in the welding and cutting power grid

In this embodiment, multiple welding and cutting power supplies, multiple welding power supplies and multiple cutting power supplies jointly form an inverter welding and cutting power supply network. Wherein, the welding and cutting power supply 61, the welding power supply 62 and the cutting power supply 63 are all connected in parallel on the DC bus 5, and the DC bus 5 is used as a common DC power supply for the welding and cutting power supply 61, the welding power supply 62 and the cutting power supply 63 DC power supply; the welding and cutting power supply 61 is used to convert the DC power supply provided by the DC bus bar 5 into another DC power supply, realizing the effect of power conversion, and the converted power is provided to the welding load or cutting load; the welding power supply 62 is used for Convert the DC power provided by the DC bus 5 into another DC power suitable for welding, and the converted power is provided to the welding load; the cutting power supply 63 is used to convert the DC power provided by the DC bus 5 into another DC suitable for cutting Power supply, the converted power is provided to the cutting load.

A welding and cutting power supply 61 provided in this embodiment is shown in Figure 4. The inverter circuit 610 includes a first switching tube Q ₁ , a second switching tube Q ₂ , a third switching tube Q ₃ , and a fourth switching tube Q ₄ , The first snubber capacitor C ₁ , the second snubber capacitor C ₂ , the third snubber capacitor C ₃ , and the fourth snubber capacitor C ₄ are respectively connected in parallel, and the first diode D ₁ , the second Diode D ₂ , third diode D ₃ , fourth diode D ₄ , the anode of the power supply is connected to the input end of the first switching tube Q ₁ and the input end of the second switching tube Q 2 , and the negative pole of the power supply is connected to the input end of the second switching tube Q ₂ . The output terminal of the fourth switching tube _Q4 is connected to the output terminal of the third switching tube _Q3 ; the output terminal of the first switching tube _Q1 is connected to the input terminal of the third switching tube _Q3 ; the input terminal of the fourth switching tube _Q4 The terminal is connected to the output terminal of the second switching transistor _Q2 . The power conversion circuit converts the DC voltage of the power supply into a periodically changing positive and negative half cycle symmetrical square wave voltage by controlling the switching state of the switching tube. As an embodiment of the present invention, the first switching tube Q ₁ , the second switching tube Q ₂ , the third switching tube Q ₃ and the fourth switching tube Q ₄ are the same, and IGBT, SiC, GaAs, etc. with higher switching frequency can be used. semiconductor power devices.

In the embodiment of the present invention, the resonant circuit 611 is composed of a resonant inductor L _r , a resonant capacitor C _r and a high-frequency isolation transformer T. One end 201 of the resonant capacitor C _r is connected to the connecting end of the first switching tube _Q1 and the third switching tube _Q3 , one end of the resonant inductance L _r is connected to the other end 202 of the resonant capacitor C _r , and the other end of the resonant inductance L _r 203 is connected to one end 204 of the primary coil of the high-frequency isolation transformer T, and the other end 205 of the primary coil is connected to the connecting end of the second switching tube _Q2 and the fourth switching tube _Q4 . Under the excitation of the output square wave voltage of the power conversion circuit, the resonant inductance L _r of the resonant circuit, the resonant capacitor C _r and the equivalent excitation inductance of the primary side of the high-frequency isolation transformer generate an approximately sinusoidal high-frequency resonant current, which passes through the high-frequency isolation transformer The primary side is transmitted to its secondary side.

In the embodiment of the present invention, the second rectification circuit 612 includes diodes _D5 and _D6 , the cathodes of diodes _D5 and _D6 are connected in parallel to the end of the filter circuit 401, and the anode of diode _D5 is connected to the secondary side of the high frequency isolation transformer T The first end 206 of the coil is connected, and the anode of the diode _D6 is connected to the third end 208 of the secondary coil of the high frequency isolation transformer T. The rectifier circuit converts the high-frequency resonant current on the secondary side of the high-frequency isolation transformer into a direct current.

In the embodiment of the present invention, the second filter circuit 613 is composed of a DC filter inductor L ₀ and a DC filter capacitor C ₀ . Terminal 401 of the filter inductor L ₀ is connected to the cathodes of the output rectifier diodes D ₅ and D ₆ , and the other terminal is connected to terminal 402 of the DC filter capacitor C0. The other end 403 of the filter capacitor _C0 is connected to the center tap 207 end of the secondary side of the high frequency isolation transformer T. The filter circuit provides a stable DC power supply for the load by suppressing the fluctuation of the DC current output by the rectifier circuit.

The embodiment provided by the present invention is designed as a welding and cutting network system based on a DC bus structure with a maximum output power of 45kW. The three-phase AC voltage input by the system is 380V, 50hz, and the output voltage of the DC bus is 400V-472V. The input power factor is greater than 0.94, and the input current THD is lower than 3% under half-load conditions.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. a welding and cutting network system based on DC busbar structure, is characterized in that, comprises electric network (1), EMI filter (2), the first filtering circuit (3), the first rectifying circuit (4), DC busbar ( 5) and inverter power supply circuit (6); The input end of the EMI filter (2) is connected to the output end of the power grid (1), and the EMI filter (2) is used to suppress high-frequency interference signals in the circuit and improve the electromagnetic compatibility performance of the system; The input end of the first filter circuit (3) is connected to the output end of the EMI filter (2), and the first filter circuit (3) is used to further filter harmonic Wave; The input end of the first rectification circuit (4) is connected to the output end of the first filter circuit (3), and the first rectification circuit (4) is used to filter the harmonic wave of the three-phase AC voltage source converted into a DC voltage source and provided to the DC bus (5); The input end of the DC bus (5) is connected to the output end of the first rectifier circuit (4), and the output end of the DC bus (5) is connected to the inverter power circuit (6); the DC bus (5) is used to provide DC power for the inverter power supply circuit (6). 2. The welding and cutting network system according to claim 1, characterized in that, the first filter circuit (3) comprises a three-phase input inductance (31), a first harmonic filter (32), a second harmonic filter device (33) and the third harmonic filter (34); One end of the three-phase input inductance (31) is connected to the output of the EMI filter, and the other end of the three-phase input inductance (31) is used as the output end of the first filter circuit (3); The first harmonic filter (32), the second harmonic filter (33) and the third harmonic filter (34) are sequentially connected in parallel on the three-phase output line of the first filter circuit (3). 3. welding and cutting network system as claimed in claim 2 is characterized in that, the first harmonic filter (32), the second harmonic filter (33) and the third harmonic filter (34) The circuit structure is the same; the first harmonic filter (32) includes a first inductance, a second inductance, a third inductance, a first capacitor, a second capacitor and a third capacitor; one end of the first inductance, the One end of the second inductance and one end of the third inductance are sequentially connected to the three-phase output line of the first filter circuit (3); One end of the third capacitor is connected to the other end of the first inductor, and the other end of the third capacitor is connected to the other end of the third inductor; The first capacitor and the second capacitor are sequentially connected in series and then connected in parallel with the third capacitor, and the parallel connection end of the first capacitor and the second capacitor is connected to the other end of the second inductor. 4. The welding and cutting network system according to any one of claims 1-3, characterized in that, the inverter power circuit (6) is used to convert the DC power provided by the DC bus (5) into welding Or the welding power supply (61) of the voltage and current required by the cutting working condition, the welding power supply (62) for converting the DC power supply provided by the DC bus (5) into the voltage and current required by the welding working condition or/and A cutting power supply (63) for converting the DC power provided by the DC bus (5) into the voltage and current required by the cutting working condition. 5. The welding and cutting network system according to claim 4, characterized in that, the welding and cutting power supply (61) comprises an inverter circuit (610), a resonant circuit (611), and a second rectifier circuit (612) connected in sequence and a second filtering circuit (613). 6. The welding and cutting network system according to claim 5, characterized in that, the inverter circuit (610) converts the DC voltage of the power supply into a periodically changing positive and negative half-cycle symmetrical square by controlling the switching state of the switching tube. Wave voltage; including the first switching tube Q ₁ , the second switching tube Q ₂ , the third switching tube Q ₃ , the fourth switching tube Q ₄ , and the first buffer capacitor C ₁ connected in parallel with the first switching tube Q ₁ , the second buffer capacitor C ₂ connected in parallel with the second switch tube Q ₂ , the third buffer capacitor C ₃ connected in parallel with the third switch tube Q ₃ , connected in parallel with the fourth switch tube Q ₄ The fourth buffer capacitor C ₄ , the first diode D ₁ connected in antiparallel to the first switching transistor Q ₁ , the second diode D ₂ connected in antiparallel to the second switching transistor Q ₂ , A third diode D ₃ connected in antiparallel to the third switching transistor Q ₃ and a fourth diode D ₄ connected in antiparallel to the fourth switching transistor Q ₄ ; The input terminal of the first switching tube _Q1 and the input terminal of the second switching tube _Q2 are connected to the positive pole of the power supply, the output terminal of the fourth switching tube _Q4 is connected to the output terminal of the third switching tube _Q3 connected to the negative pole of the power supply; The output end of the first switching transistor _Q1 is connected to the input end of the third switching transistor _Q3 ; the input end of the fourth switching transistor _Q4 is connected to the output end of the second switching transistor _Q2 . 7. The welding and cutting network system according to claim 6, characterized in that, the first switching tube Q ₁ , the second switching tube Q ₂ , the third switching tube Q ₃ and the fourth switching tube The same as the tube _Q4 , which is a semiconductor power device with a relatively high switching frequency such as IGBT, SiC, and _GaAs . 8. welding and cutting network system as claimed in claim 5, is characterized in that, described resonant circuit (611) comprises resonant inductance L _r , resonant capacitor C _r and high-frequency isolation transformer T; One end of the resonant capacitor C _r is connected to the connecting end of the first switching tube _Q1 and the third switching tube _Q3 , one end of the resonant inductance L _r is connected to the other end of the resonant capacitor C _r , and the other end of the resonant inductance L _r One end of the primary coil of the high-frequency isolation transformer T is connected, and the other end of the primary coil is connected to the connection end of the second switching tube _Q2 and the fourth switching tube _Q4 ; Under the excitation of the square wave voltage, the resonant inductance L _r , the resonant capacitor C _r and the equivalent excitation inductance of the primary side of the high-frequency isolation transformer generate an approximately sinusoidal high-frequency resonant current, which passes through the primary side of the high-frequency isolation transformer edge is transmitted to its secondary edge. 9. welding and cutting network system as claimed in claim 8, is characterized in that, described second rectifier circuit (612) converts the high-frequency resonant current of high-frequency isolation transformer secondary side into direct current; Described second rectifier circuit (612) including diode _D5 and diode _D6 ; The cathodes of the diode D ₅ and the diode D ₆ are connected in parallel as the output end of the second rectifier circuit (612), the anode of the diode D ₅ is connected to the first end of the secondary coil of the high-frequency isolation transformer T, and the diode D ₆ The anode of the anode is connected to the third end of the secondary coil of the high frequency isolation transformer T, and the second end of the secondary coil of the high frequency isolation transformer T is grounded. 10. The welding and cutting network system as claimed in claim 5, characterized in that, the second filter circuit (613) provides a stable DC power supply for the load by suppressing the fluctuation of the output DC current of the second rectifier circuit; The second filter circuit (613) includes a DC filter inductor L ₀ and a DC filter capacitor C ₀ ; One end of the DC filter inductor _L0 is used as the input end of the second filter circuit (613), the other end of the DC filter inductor _L0 is grounded through the DC filter capacitor _C0 , and the DC filter inductor _L0 The other end of is also used as the output end of the second filtering circuit (613).