CN106208745A - CUT output current ripple frequency multiplication and modulating system - Google Patents

Abstract

The present invention provides a kind of CUT output current ripple frequency multiplication and modulating system, including reduction voltage circuit, chopper circuit and cutting torch circuit, described chopper circuit includes two groups of BUCK circuit, is connected with the workpiece to be processed of cutting torch circuit after two groups of BUCK circuit output end parallel connections.The present invention is by designing discontinuous sawtooth carrier wave, the break-make of respective four IGBT module of the PWM drive signal control two-way BUCK circuit of equal duty ratio is produced when stable state, the IGBT module trigger sequence of each of which road BUCK circuit differs 90 ° successively, make the DC current ripple quadruple on each road, two-way output differs certain angle 45 ° according to actual condition, complementing each other so that the DC current output ripple octonary of synthesis, ripple current amplitude reduces further.The present invention support output current ripple frequency multiplication, single tube IGBT stress little, can modularized design and support High-current output, and control principle is clear, control signal occurs simple.

Description

Plasma cutting machine output current ripple frequency multiplication and modulation system

technical field

The present invention relates to an output current ripple reduction technology in the fields of plasma cutting and power electronic conversion, and in particular relates to a frequency multiplication and modulation system for output current ripple of a plasma cutting machine.

Background technique

"Cutting and welding" is known as "steel tailoring". Modern industry is inseparable from the cutting and welding of sheet metal. Cutting is the first process of welding. The quality of the cut section (flatness, smoothness), cutting efficiency and The level of material utilization directly affects welding quality (such as welding strength), production efficiency and cost. Therefore, the development of modern industry is inseparable from modern metal profile cutting and processing equipment. At present, there are three main methods for cutting metal profiles: flame, plasma, and laser. Plasma cutting is efficient and low-cost, and it is the most ideal choice for profile cutting. It has been widely used in many fields of industrial production. application.

The plasma cutting power supply is one of the core components of the machine plasma cutting device. In view of the lower overall cost and higher efficiency, in the high-power plasma cutting device, the chopping power supply is increasingly favored, and the power circuit supports the continuous increase of the output current level. . On the other hand, the industry has higher and higher requirements for the quality of DC power supply (including voltage stability, peak-to-peak ripple frequency, and ripple frequency), and relying solely on passive components (increasing capacitance and inductance) can no longer meet the needs of the industry. . Therefore, high-power design and high-frequency output current ripple are problems to be solved urgently for the plasma cutting DC source.

After searching the existing technology of the output current ripple frequency modulation method of the plasma cutting machine, it is found that there are mainly the following representative documents:

The article "Design of DC Current Source for Plasma Cutting Machine" puts forward a scheme to increase the power level of plasma power supply with two BUCK outputs, but the DC output ripple frequency of this circuit is relatively high, which cannot meet the higher level of output current accuracy requirements. The article "Research on High-Performance Power Supply System for Plasma Cutting" proposes a buffered BUCK converter to reduce sudden changes in voltage and current, but this circuit is not suitable as a power supply for plasma cutting machines with high power levels and high precision requirements.

Based on the above, after searching the prior art of the frequency multiplication modulation method of the output current ripple of the plasma cutting machine, it is found that the existing control method lacks a control strategy that can effectively increase the ripple frequency.

Contents of the invention

In view of the defects in the prior art, the purpose of the present invention is to provide a plasma cutting machine output current ripple frequency multiplication and modulation system, which can effectively increase the ripple frequency.

According to the first aspect of the present invention, a plasma cutting machine output current ripple frequency multiplication system is provided, including a step-down circuit, a chopper circuit and a cutting torch circuit, wherein: the step-down circuit is used to complete the three-phase AC voltage transformation; the chopper circuit is used to synthesize a stable direct current; the cutting torch circuit is used to complete fine cutting.

Preferably, the step-down circuit includes a power frequency transformer, wherein: the input ends of the three-phase primary windings of the power frequency transformer are respectively connected to a three-phase AC power supply of 380V, and its secondary includes two sets of three-phase secondary windings with a difference of 30° The primary winding is 220V, and the initial phases of the three-phase secondary winding are Y connected to 0° and Δ connected to 30° respectively.

Preferably, the chopping circuit includes two groups of BUCK circuits, namely a first BUCK circuit and a second BUCK circuit, the output ends of the first BUCK circuit and the second BUCK circuit are connected in parallel to the workpiece to be processed in the cutting torch circuit.

The first BUCK circuit includes: a first diode uncontrolled three-phase rectifier bridge, a first electrolytic capacitor, a first power resistor, a first IGBT module, a second IGBT module, a third IGBT module, a fourth IGBT module, The first reverse fast recovery power diode, the second reverse fast recovery power diode, the third reverse fast recovery power diode, the fourth reverse fast recovery power diode and the first smoothing inductor, wherein: the first diode is not The input of the controlled three-phase rectifier bridge is the output Ua1, Ub1 and Uc1 of the Y-connected 0° three-phase secondary winding in the step-down circuit, the first diode does not control the DC output positive pole of the three-phase rectifier bridge and the first electrolytic capacitor positive pole, one end of the first power resistor, first reverse fast recovery power diode cathode, second reverse fast recovery power diode cathode, third reverse fast recovery power diode cathode, fourth reverse fast recovery power diode cathode, the first reverse fast recovery power diode cathode, One end of a smoothing inductor is connected, the first diode does not control the DC output negative pole of the three-phase rectifier bridge, the negative pole of the first electrolytic capacitor, the other end of the first power resistor, the emitter of the first IGBT module, the second IGBT The emitter of the module, the emitter of the third IGBT module, and the emitter of the fourth IGBT module are connected, the collector of the first IGBT module, the collector of the second IGBT module, the collector of the third IGBT module, and the fourth IGBT module The collector of the first reverse fast recovery power diode anode, the second reverse fast recovery power diode anode, the third reverse fast recovery power diode anode, and the fourth reverse fast recovery power diode anode are connected to form the negative pole of the DC power supply , the other end of the first smoothing inductor forms the positive pole of the DC power supply;

The second BUCK circuit includes: a second diode uncontrolled three-phase rectifier bridge, a second electrolytic capacitor, a second power resistor, a fifth IGBT module, a sixth IGBT module, a seventh IGBT module, an eighth IGBT module, The fifth reverse fast recovery power diode, the sixth reverse fast recovery power diode, the seventh reverse fast recovery power diode, the eighth reverse fast recovery power diode and the second smoothing reactor, wherein: the second diode The three-phase input of the uncontrolled three-phase rectifier bridge is the output Ua2, Ub2 and Uc2 of the 30° three-phase secondary winding in the step-down circuit, and the DC output positive pole of the second diode uncontrolled three-phase rectifier bridge is connected to the second The positive pole of the electrolytic capacitor, one end of the second power resistor, the fifth reverse fast recovery power diode cathode, the sixth reverse fast recovery power diode cathode, the seventh reverse fast recovery power diode cathode, the eighth reverse fast recovery power diode The cathode and one end of the second smoothing inductor are connected, the second diode does not control the DC output negative pole of the three-phase rectifier bridge, the negative pole of the second electrolytic capacitor, the other end of the second power resistor, the emitter pole of the fifth IGBT module, and the negative pole of the second electrolytic capacitor. The emitter of the sixth IGBT module, the emitter of the seventh IGBT module, the emitter of the eighth IGBT module, the collector of the fifth IGBT module, the collector of the sixth IGBT module, the collector of the seventh IGBT module, the collector of the eighth IGBT module and the fifth The anode of the reverse fast recovery power diode, the anode of the sixth reverse fast recovery power diode, the anode of the seventh reverse fast recovery power diode, and the anode of the eighth reverse fast recovery power diode are connected to form the negative pole of the DC power supply, and the second smoothing inductor The other end forms the positive pole of the DC power supply;

The torch circuit is connected to two output terminals of two BUCK circuits, wherein: one end of the workpiece to be processed is connected to the positive pole of the chopper circuit, the other end of the workpiece to be processed is connected to one end of the plasma arc column, and the other end of the plasma arc column It is connected with the torch bumper and the internal electrode, and the negative pole of the cutting torch circuit is connected with the negative pole of the chopper circuit.

According to the second aspect of the present invention, there is provided a modulation system of the output current ripple frequency multiplication system of the plasma cutting machine, including a filter unit, a desired current comparison unit, a fractional PID adjustment unit, a limiting unit, a carrier comparison unit and a pole A polarity judgment unit, wherein: the carrier comparison unit includes first to eighth carrier comparison units; the polarity judgment unit includes first to eighth polarity judgment units;

The sampled output current signal of the cutting machine in operation, that is, the total current signal io output by the two BUCK circuits, is sent to the filter unit, and the output current filtered by the filter unit is input to the expected current comparison unit, and the expected current comparison unit converts the output current The current error is obtained by subtracting the expected current corresponding to the desired actual output current. The current error is input to the fractional-order PID adjustment unit, and the fractional-order PID adjustment unit performs proportional integral differential adjustment on the current error. The output of the fractional-order PID adjustment unit and the limiter unit Connected, the limiting unit ensures that the fractional-order PID adjustment output is limited between the specified upper and lower limits to prevent overflow and underflow. The output of the limiting unit is used as one input of the first carrier to the eighth carrier comparison unit, and the other input The first to eighth carrier waves are compared separately, that is, the fractional-order PID adjustment output is compared with the carrier wave, and the compared 8-way results are respectively input to the first to eighth polarity judgment units, and the first to eighth polarity Judgment unit for polarity judgment: output high level when the compared 8-way results are positive, output low level when the compared 8-way results are negative, the outputs of the first to eighth polarity judgment units generate the first to eighth polarity judgment units. The eighth PWM driving signal, the eight PWM driving signals respectively drive the on-off of the first to eighth IGBT modules in the BUCK circuit to complete the conversion from the output voltage to the output current.

The present invention controls the on-off of the eight IGBT modules of the two BUCK circuits through PWM driving signals with equal duty ratios, wherein the trigger sequence of each IGBT module is sequentially different by 90°, so that the frequency of the DC current ripple of each path is multiplied by 4, and the two The two outputs differ by a certain angle of 45° according to the actual working conditions, and complement each other so that the synthesized DC current output current ripple frequency is 8 times the frequency, and the current ripple is further reduced.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The four IGBT modules of each BUCK circuit adopt a phase-shift control strategy, and the phase is shifted by 90°, so that the output current ripple of each channel is multiplied by 4;

(2) The two BUCK circuits complement each other and shift the phase by 45°, so that the output current ripple of the output is multiplied by 8, and the output current ripple is lower;

(3) Eight IGBT modules share the power output, which can support large current output and the single-tube power stress is small;

(4) The four IGBT modules of each BUCK circuit share one smoothing inductor, which saves components and reduces the volume of the power supply;

(5) The emitter of the IGBT module is connected to the negative pole of the rectifier output, which makes the design of the driving circuit more convenient.

The invention adopts the equal duty cycle phase-shifting control strategy to make each output current ripple frequency multiplied, and effectively reduce the synthesized output current ripple, current ripple multiplied frequency, single-tube IGBT stress is small, modular design and support Large current output has the advantages of clear control principle and simple control signal generation.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a circuit diagram of a frequency multiplication system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a modulation system according to an embodiment of the present invention.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

As shown in Figure 1, this embodiment provides a plasma cutting machine output current ripple frequency multiplication modulation system, including a step-down circuit 11, a chopper circuit and a cutting torch circuit 14, wherein: the step-down circuit is used to complete three Phase-to-phase alternating voltage conversion; the chopper circuit is used to synthesize a stable direct current; the cutting torch circuit is used to complete fine cutting.

As shown in Figure 1, the step-down circuit 11 includes a power frequency transformer, wherein: the input ends of the three-phase primary windings of the power frequency transformer are respectively connected to the three-phase AC power supply 380V, and its secondary includes two groups with a phase difference of 30° The three-phase secondary winding of the three-phase secondary winding is 220V, and the initial phases of the three-phase secondary winding are Y connected to 0° and Δ connected to 30°, which are used to realize the voltage transformation of 380V-220V.

As shown in FIG. 1, the chopper circuit includes two groups of BUCK circuits, which are respectively a first BUCK circuit 12 and a second BUCK circuit 13;

The first BUCK circuit 12 includes: a diode uncontrolled three-phase rectifier bridge B1, an electrolytic capacitor E1, a power resistor R1, four IGBT modules S1-S4, and four reverse fast recovery power diodes D1- D4 and a smoothing reactor L1, wherein: the three-phase input of the diode uncontrolled three-phase rectifier bridge B1 is the output ua1, ub1 and uc1 of the 0° three-phase secondary winding in the step-down circuit 11, and the diode is uncontrolled The positive pole P1 of the DC output of the three-phase rectifier bridge B1 is connected to the positive pole of the electrolytic capacitor E1, one end of the power resistor R1, the cathodes of the reverse fast recovery power diodes D1-D4, and one end of the smoothing inductor L1, and the diode is not controlled by the three-phase rectifier bridge B1 The DC output negative electrode N1 of the DC output is connected to the negative electrode of the electrolytic capacitor E1, the other end of the power resistor R1, and the emitters of the IGBT modules S1-S4, and the collectors of the IGBT modules S1-S4 are connected to the anodes of the reverse fast recovery power diodes D1-D4. Form the negative pole of the DC power supply, and the other end of the smoothing inductor L1 forms the positive pole of the DC power supply;

The second BUCK circuit 13 includes: a diode uncontrolled three-phase rectifier bridge B2, an electrolytic capacitor E2, a power resistor R2, four IGBT modules S5-S8, and four reverse fast recovery power diodes D5- D8 and a smoothing reactor L2, wherein: the three-phase input of the diode uncontrolled three-phase rectifier bridge B2 is the output ua2, ub2 and uc2 of the 30° three-phase secondary winding in the step-down circuit 11, and the diode is uncontrolled The DC output positive pole P2 of the three-phase rectifier bridge B2 is connected to the positive pole of the electrolytic capacitor E2, one end of the power resistor R2, the cathodes of the reverse fast recovery power diodes D5-D8, and one end of the smoothing inductor L2, and the diode does not control the three-phase rectifier bridge B2 The DC output negative electrode N2 of the DC output is connected to the negative electrode of the electrolytic capacitor E2, the other end of the power resistor R2, and the emitter of the IGBT module S5-S8, and the collector of the IGBT module S5-S8 is connected to the anode of the reverse fast recovery power diode D5-D8. Form the negative pole of the DC power supply, and the other end of the smoothing inductor L2 forms the positive pole of the DC power supply;

The output ends of the first BUCK circuit and the second BUCK circuit are connected in parallel to the workpiece of the cutting torch circuit 14, wherein the workpiece is connected to the positive pole of the chopping circuit, and the negative pole of the cutting torch circuit is connected to the negative pole of the chopping circuit.

As shown in Figure 2, a modulation system of the above-mentioned frequency multiplication system, by designing a discontinuous sawtooth carrier, generates a PWM drive signal with an equal duty cycle in a steady state to control the communication of the four IGBT modules of the two BUCK circuits. The trigger sequence of the IGBT modules of each BUCK circuit differs by 90° in sequence, so that the DC current ripple of each path is quadrupled, and the two outputs differ by a certain angle of 45° according to the actual working conditions. The ripple frequency is eight times higher, and the ripple current amplitude is further reduced.

A modulation system of the above-mentioned frequency multiplication system, comprising a filter unit, a desired current comparison unit, a fractional-order PID adjustment unit, a limiting unit, and a carrier comparison unit (two inputs 1, 2 and an output 3 of the carrier comparison unit in Fig. 2 ), the polarity judgment unit and the PWM generation unit, the current signal obtained by sampling is sent to the filter unit, the output of the filter unit is subtracted from the expected current, and the obtained current error is input to the fractional-order PID adjustment unit, and the output of the fractional-order PID adjustment unit and the limiter The units are connected, and the output of the limiting unit is compared with the carrier 1-8 respectively, and the compared results are respectively connected with the polarity judging unit 1-8, and the output of the polarity judging unit 1-8 generates PWM1-8 respectively. The PWM control signals of the first BUCK circuit 12 differ by 90°, specifically: PWM1 leads PWM2 by 90°, PWM2 leads PWM3 by 90°, PWM3 leads PWM4 by 90°, and the output current ripple of this circuit is quadrupled in frequency; the second BUCK circuit The PWM control signals of 13 have a difference of 90°, specifically: PWM5 leads PWM6 by 90°, PWM6 leads PWM790°, PWM7 leads PWM8 by 90°, and the output current ripple frequency of this channel is quadruple; PWM1 and PWM5 will differ according to the working conditions of the circuit At one angle, the output currents of the two BUCK circuits complement each other, so that the ripple of the synthesized output current i _o is further reduced, so as to realize fine and large current output and meet the DC power requirements of the plasma cutting machine.

In a certain embodiment, the selection and parameters of each device are:

AC input voltage wide range, 380V±15%, power frequency 50Hz or 60Hz, rated input voltage 380VAC, rated output DC voltage average 150V, rated output current 270A, input power 45kW;

IGBT chopping frequency: 20kHz;

Electrolytic capacitors E1-E2: 450V, 6800μF, four in parallel;

Diode uncontrolled three-phase rectifier bridge B1-B2: 600V, 300A/100℃;

Smoothing reactor L1-L2: 2.2mH, 130A, 0.35mm thick, silicon steel;

IGBT module and reverse fast recovery power diode S1 and D1, S2 and D2, S3 and D3, S4 and D4, S5 and D5, S6 and D6, S7 and D7, S8 and D8: 600V, 250A/100℃, single bridge arm IGBT module;

Power resistor R1-R2: 50kΩ, 5W;

Power frequency transformer TR1: 380V/2x220V, 75kVA.

Key principles of the present invention are:

(1) Carrier phase-shift driving technology, the driving signals of 4 IGBT modules in each BUCK circuit are staggered by 90°, and the driving signals of 8 IGBT modules in two BUCK circuits are staggered by 45°, which can effectively reduce the smoothing inductance of each size and reduce current ripple;

(2) Special carrier design, as shown in Figure 2, in the steady state, the driving signal of each IGBT module is generated by comparing the discontinuous sawtooth carrier with the control signal, and has the same Duty cycle, after comparison, the polarity is positive, generates high level, drives the corresponding IGBT module to turn on, and after comparison, the polarity is negative, generates low level, drives the corresponding IGBT module to turn off; in dynamic state, each The driving signal of the IGBT module is generated by comparing the discontinuous sawtooth carrier with the control signal, and the duty cycle changes in real time;

(3) The carrier phase-shift driving technology with equal duty ratio is different from the traditional carrier phase-shift driving technology. 1/4, each BUCK circuit cannot realize the frequency multiplication function, the final output current ripple of the two BUCK circuits is only 2 times the frequency, only when the duty ratio is less than 1/4, each BUCK circuit can realize the frequency multiplication function , the final output current ripple is multiplied by 8. When the output voltage is high, especially for the application of plasma gas cutting machine, the duty cycle is greater than 0.5 but less than 0.6, so the present invention can achieve 8 times the frequency of the output current under any working conditions, and can improve the frequency of the output current without changing the carrier frequency DC inductor current ripple frequency, thereby improving the current fineness, improving the cutting quality of the workpiece, and can also increase the output power level; or maintain the DC inductor current ripple frequency unchanged, thereby reducing the carrier frequency, reducing the switching loss of the IGBT module, and This increases the power level.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (4)

1. a CUT output current ripple frequency doubling system, including reduction voltage circuit, chopper circuit and cutting torch circuit, its In: described reduction voltage circuit is in order to complete the conversion of three-phase alternating voltage；The direct current that described chopper circuit is stable in order to synthesize a road Electric current；Described cutting torch circuit is in order to complete fine cut；It is characterized in that:

Described reduction voltage circuit includes an Industrial Frequency Transformer, wherein: the input of described Industrial Frequency Transformer three-phase primary windings divides Not being connected with three-phase alternating-current supply, its secondary includes the three-phase secondary windings of two groups of differences 30 °, and the first phase of three-phase secondary windings is divided Do not connect 0 ° for Y and Δ connects 30 °；

Described chopper circuit includes two groups of BUCK circuit, is a BUCK circuit and the 2nd BUCK circuit respectively, a BUCK electricity It is connected with the workpiece to be processed of cutting torch circuit after road, the 2nd BUCK circuit output end parallel connection；

A described BUCK circuit includes: the first diode do not control three-phase commutation bridge, the first electrochemical capacitor, the first power resistor, First IGBT module, the second IGBT module, the 3rd IGBT module, the 4th IGBT module, first reversely recover soon power diode, Second reversely recover soon power diode, the 3rd reversely recover soon power diode, the 4th the fastest recover power diode and First flat ripple inductance, wherein: it is that in reduction voltage circuit, Y connects 0 ° of three-phase secondary windings that the first diode does not control the input of three-phase commutation bridge Output Ua1, Ub1 and Uc1, the first diode is not just controlling the direct current output cathode of three-phase commutation bridge and the first electrochemical capacitor Pole, one end of the first power resistor, the first reverse power diode negative electrode of recovery soon, second the fastest recovery power diode the moon Pole, the 3rd reversely fast recover power diode negative electrode, the 4th the fastest recover power diode negative electrode, the one of the first flat ripple inductance End is connected, and the first diode does not control direct current output negative pole and the negative pole of the first electrochemical capacitor, the first power electricity of three-phase commutation bridge The other end of resistance, the emitter stage of the first IGBT module, the emitter stage of the second IGBT module, the emitter stage of the 3rd IGBT module, the The emitter stage of four IGBT module is connected, the colelctor electrode of the first IGBT module, the colelctor electrode of the second IGBT module, the 3rd IGBT module Colelctor electrode, the colelctor electrode of the 4th IGBT module and first reversely fast recover power diode anode, second reversely recover merit soon Rate diode anode, the 3rd the fastest recovery power diode anode, the 4th the fastest power diode anode that recovers are connected, shape Becoming the negative pole of DC source, the other end of the first flat ripple inductance forms the positive pole of DC source；

Described 2nd BUCK circuit includes: the second diode do not control three-phase commutation bridge, the second electrochemical capacitor, the second power resistor, 5th IGBT module, the 6th IGBT module, the 7th IGBT module, the 8th IGBT module, the 5th reversely recover soon power diode, 6th reversely recover soon power diode, the 7th reversely recover soon power diode, the 8th the fastest recover power diode and Second smoothing reactor, wherein: the second diode is not controlled the three-phase input of three-phase commutation bridge and connect 30 ° of three-phases for Δ in reduction voltage circuit Output Ua2, Ub2 and Uc2 of secondary windings, the second diode does not control direct current output cathode and the second electrolysis electricity of three-phase commutation bridge The positive pole of appearance, one end of the second power resistor, the 5th reverse fast recovery power diode negative electrode, the 6th reverse recovery power two soon Pole tube cathode, the 7th reverse fast recovery power diode negative electrode, the 8th the fastest recovery power diode negative electrode, the second flat ripple electricity One end of sense is connected, the second diode do not control the direct current output negative pole of three-phase commutation bridge and the negative pole of the second electrochemical capacitor, second The other end of power resistor, the 5th IGBT module emitter stage, the 6th IGBT module emitter stage, the 7th IGBT module emitter stage, Eight IGBT module emitter stages, the 5th IGBT module colelctor electrode, the 6th IGBT module colelctor electrode, the 7th IGBT module colelctor electrode, Eight IGBT module colelctor electrodes and the 5th reversely fast recover power diode anode, the 6th the fastest recover power diode anode, 7th the fastest recovery power diode anode, the 8th the fastest power diode anode that recovers are connected, formation DC source Negative pole, the other end of the second flat ripple inductance forms the positive pole of DC source.

CUT output current ripple frequency doubling system the most according to claim 1, it is characterised in that described cutting torch Circuit is connected, wherein with two outfans of two-way BUCK circuit: workpiece one end to be processed is connected with the positive pole of chopper circuit, The workpiece other end to be processed is connected with plasma column one end, and the plasma column other end and cutting torch touch mouth and internal electrode phase Even, the negative pole of cutting torch circuit is connected with the negative pole of chopper circuit.

3. a modulating system for CUT output current ripple frequency doubling system described in claim 1 or 2, its feature exists In, including filter unit, expectation electric current comparing unit, Fractional Order PID regulation unit, clipping unit, carrier wave comparing unit and pole Property judging unit, wherein: carrier wave comparing unit includes first～the 8th carrier wave comparing unit；Polarity judging unit include first～ Ends of the earth property judging unit；

Cutting machine output current signal in the operation of sampling gained, i.e. the total current signal io of two-way BUCK circuit output, sends into Filter unit, the output electric current input expectation electric current comparing unit after filtered unit filtering, it is desirable to electric current comparing unit should Output electric current obtains current error with the corresponding expectation current subtraction wishing actual output current, this current error input fractional order PID regulates unit, and Fractional Order PID regulation unit carries out PID regulation, Fractional Order PID regulation unit to current error Output be connected with clipping unit, clipping unit guarantees that Fractional Order PID regulation export-restriction is being specified between bound, prevents out Existing overflow and underflow, the output of clipping unit carries～an input of the 8th carrier wave comparing unit as first, its another input Be respectively first～the 8th carrier wave, compare respectively, i.e. Fractional Order PID regulation output carries out size with carrier wave and compares, and compares After 8 tunnel results input respectively first～ends of the earth property judging unit, first～ends of the earth property judging unit carry out polarity judgement: 8 tunnel results after Bi compare are that timing exports high level, and 8 tunnel results after comparing are output low level, first～the ends of the earth time negative Property judging unit output produce first～the 8th PWM drive signal, eight PWM drive signal drive in BUCK circuit the respectively The break-make of the one～the 8th IGBT module, completes the output voltage conversion to output electric current.

Modulating system the most according to claim 3, it is characterised in that control two by the PWM drive signal of equal duty ratio The break-make of eight IGBT module of road BUCK circuit, each of which road IGBT module trigger sequence differs 90 ° successively so that each DC current ripple 4 frequency multiplication on road, two-way output differs certain angle 45 ° according to actual condition, complements each other so that synthesis DC current output current ripple frequency 8 frequency multiplication, current ripples reduces further.