CN115864847A - High-power torch power supply applied to plasma - Google Patents
High-power torch power supply applied to plasma Download PDFInfo
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Abstract
The invention discloses a high-power torch power supply applied to plasma, which relates to the technical field of plasma, and is improved based on the existing high-power torch power supply, a controllable direct-current power loop is additionally arranged, the controllable direct-current power loop is matched with a main power loop to adapt to different stages of plasma production, and in the plasma generation stage, no-load voltage of the loop is connected with direct-current power in series to avoid redundancy of a plurality of power loops, so that the application range of the high-power torch power supply is expanded; in the plasma arc stabilizing stage, the direct current power loop inhibits the increasing rate of the current; in the plasma discharge maintaining stage, the conduction voltage drop of the direct current power loop is small, and the heat loss is reduced; in the plasma minactization stage, the direct-current power loop plays a role of power inductance, and the effect of larger inductance can be equivalent through algorithm presetting; through the action of the controllable direct current power loops at different stages, the load adaptability, the volume weight, the output dynamic characteristics and the like of the power supply of the high-power torch are improved conveniently.
Description
Technical Field
The invention relates to the technical field of plasmas, in particular to a high-power torch power supply applied to plasmas.
Background
With the rapid development of industrialization in China, the thermal plasma melting technology has great advantages in the application directions of treating dangerous waste, medical infected garbage, chemical and heavy metal polluted garbage and the like. For example, in view of the above, the thermal plasma fusion technique has the outstanding advantages of high treatment temperature, many suitable types, small secondary pollution, and the like, and is widely used.
With the application and popularization of the thermal plasma fusion technology, the output power of the plasma torch power supply is larger and larger. For an ultra-large scale power supply system, it is often necessary to realize an output current of approximately kilo amperes and an output power of approximately megawatts. The high-power torch power supply is used as an important component of the thermal plasma melting technology, and the stability and reliability of the performance of the power supply are important guarantees for the thermal plasma melting application. The working process of the thermal plasma melting is divided into four stages.
The first stage is a plasma generation stage. The high-voltage trigger excitation generates an electric field to accelerate the movement of gas particles, and plasma is generated through ionization. The trigger excitation voltage described above is related to the distance between the anode and the cathode, the gas composition, the gas flow rate, and the like. The longer the distance between the cathode and the anode, the higher the required trigger excitation voltage; the more difficult the gas component to ionize, the higher the trigger excitation voltage, the power loop no-load voltage, is required. For example, when nitrogen gas ionized in the atmosphere is compared with argon gas ionized in vacuum, the trigger excitation voltage is five times higher than that of the argon gas ionized in vacuum, and the higher the no-load voltage of the power loop is, the easier the trigger excitation and the arc stabilization are realized. In this case, in order to reduce the difficulty of plasma generation, a plurality of electrodes are often added and an arc-turning circuit is provided. In order to meet the change of the application scenes, the plasma torch power supply needs to have certain power redundancy, and for an ultra-large-scale power supply system, the power redundancy is avoided.
The trigger excitation voltage at this stage is high, above several kilovolts, but its power is small, below hundred watts. Through the high-voltage triggering excitation at the stage, the cathode and the anode form a plasma channel, the no-load of the power loop is changed into the load, and the output current is rapidly increased. Under the influence of the above factors, the magnitude of the no-load voltage of the power loop at this stage will directly influence whether the plasma channel is rapidly broken down and whether the output current can be rapidly increased.
The second stage is an arc stabilization stage. The output current of the power loop is rapidly increased until the current is nearly hundreds of amperes and is stably maintained, and the plasma can not form a stable arc loop. Often, this stage is still accompanied by high voltage trigger excitation, the load impedance changes dramatically, and the power supply system needs to have a fast dynamic response capability to adjust and stabilize the output current, and simultaneously avoid electrode ablation caused by overcurrent. The high no-load voltage of the power loop at this stage is beneficial to stabilizing electric arcs, and the good current limiting effect of the output loop is beneficial to inhibiting ablation.
The third stage is the maintenance stage. The output voltage and the output current of the plasma torch power supply at the later stage of the process are gradually increased, and the conduction loss of a power device is in direct proportion to the square of the current. The reduction of the conduction loss is of great significance.
The fourth stage is the minactine stage. This stage is not a mandatory stage of the plasma torch operation. Because the plasma impedance is obviously changed due to the change of the species and components of the dangerous waste, the gas component flow and the like in the process, if the power supply can not respond quickly, the normal discharge state can not be maintained, the plasma is extinguished, and the process is forced to stop. In order to avoid the situation, the power supply of the high-power plasma torch is connected with a power inductor with larger inductance in series at the output end. However, for a super-large-scale power supply system, the power inductor with large current and large inductance has high manufacturing cost, large volume and large heat loss. The avoidance of large-capacity power inductance is of great significance.
The traditional high-power plasma torch power supply is usually formed by connecting a plurality of power loops in parallel to output high current and high power, and cannot adapt to each working stage of the plasma torch. Resulting in power redundancy, higher cost, increased volume and weight of the high power plasma torch power supply, and also having extremely high requirements on the loop stability of the power supply.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the conventional high-power plasma torch power supply is usually formed by connecting a plurality of power loops in parallel to output high current and high power, and cannot be well adapted to each stage of a plasma torch. The invention aims to provide a high-power torch power supply applied to plasma, which is improved based on the existing high-power torch power supply, a controllable direct-current power loop is additionally arranged, and the problems occurring in each working stage of a torch are optimized through the cooperation of the controllable direct-current power loop and a main power loop.
The invention is realized by the following technical scheme:
the scheme provides a high-power torch power supply applied to plasma, which comprises a controllable direct-current power loop and a plurality of power loops; the plurality of power loops are connected in parallel to form a main power loop, and the controllable direct current power loop is connected in series with the main power loop;
in the plasma generation stage, the controllable direct current power loop is connected with the power loop in series to increase the no-load voltage, so that the plasma generation device is suitable for different torch devices and torch processes to generate plasma discharge;
in the plasma arc stabilizing stage, the controllable direct current power loop is connected with the power loop in series to improve the no-load voltage, so that the arc is stabilized quickly, and the increase rate of the current of the main power loop is inhibited;
and in the plasma maintaining stage, the controllable direct current power loop enables the conduction voltage drop of the power device to be short-circuited through the through switch. The contact resistance of the through switch is within 0.5 milliohm, and the heat loss is reduced by the measure of connecting a plurality of through switches in parallel;
in the plasma minactization stage, the controllable direct-current power loop is connected in series with the power loop to play a role of a power inductor, and the effect of larger inductance can be equivalent through algorithm presetting.
The working principle of the scheme is as follows: the traditional high-power plasma torch power supply usually outputs large current and high power in parallel by a plurality of power loops, and cannot adapt to each working stage of the plasma torch. The invention aims to provide a high-power torch power supply applied to plasma, which is improved based on the existing high-power torch power supply, a controllable direct-current power loop is additionally arranged, and the controllable direct-current power loop is matched with a main power loop to adapt to different working stages of the plasma torch; is particularly suitable for the treatment of the hazardous substances with ultra-high power scale, such as radioactive nuclear waste, waste residues containing harmful substances such as heavy metal and the like.
The further optimization scheme is that the controllable direct current power loop comprises: the direct current circuit soft switch inverter circuit, the direct current circuit power transformer, the direct current circuit high-frequency rectification filter circuit, the direct current circuit chopping power switch device, the direct current circuit follow current power switch device, the direct current circuit current-limiting resistor, the direct current circuit direct power switch device group and the direct current circuit control circuit;
the direct current power required by the direct current loop soft switching inverter circuit can be provided by an AC-DC rectifying circuit of a certain main power loop, and can also be provided by using three-phase power of a power grid after AC-DC rectification. The direct current power is output after sequentially passing through a direct current loop soft switch inverter circuit, a direct current loop power transformer and a direct current loop high-frequency rectification filter circuit, the positive electrode output end of the direct current loop high-frequency rectification filter circuit is connected with a direct current loop chopping power switch device in series and then serves as the positive electrode output end of a high-power torch power supply, and the negative electrode output end of the direct current loop high-frequency rectification filter circuit is connected with the positive electrode output end of a main power loop; after the direct current loop follow current power switch device is connected with the direct current loop current limiting resistor in series, one end of the direct current loop follow current power switch device is connected with the positive output end of the high-power torch power supply, and the other end of the direct current loop follow current power switch device is connected with the negative output end of the direct current loop high-frequency rectifying and filtering circuit; one end of the direct current loop direct connection power switch device group is connected with the positive output end of the high-power torch power supply, and the other end of the direct current loop direct connection power switch device group is connected with the negative output end of the direct current loop high-frequency rectifying and filtering circuit;
the direct current loop control circuit is respectively connected with the direct current loop soft switch inverter circuit, the direct current loop high-frequency rectification filter circuit, the direct current loop chopping power switch device, the direct current loop follow current power switch device and the direct current loop through power switch device group.
The direct current loop soft switch inverter circuit inverts the received direct current into high-frequency bipolar output to provide high-frequency alternating current input for the power transformer. The DC loop soft switch inverter circuit preferably has the same structure as the soft switch inverter circuit, and is realized by a multi-level-shifting phase full-bridge inverter circuit, a staggered serial connection two-level full-bridge phase-shifting inverter circuit or a three-level full-bridge LLC inverter circuit, so that the switching loss is reduced, the efficiency is improved, and the electromagnetic interference is reduced.
The direct current loop power transformer realizes electric energy isolation and level conversion and provides high-frequency alternating current input for the high-frequency rectification filter circuit;
the high-frequency rectifying and filtering circuit of the direct current loop rectifies high-frequency alternating current input into direct current with isolated potential. Preferably, the synchronous rectification circuit, the full-bridge rectification circuit, the full-wave rectification circuit, the half-bridge rectification current, the half-wave rectification circuit, the LC filter circuit and the capacitor filter circuit.
The direct-current loop follow current power switch device provides a follow current path for the direct-current loop chopping power switch device at the moment of turning off, and preferably has a proper on-resistance, so that when the direct-current loop follow current power switch device is turned on, the effect of reducing the voltage of the anti-parallel diode can be achieved.
The direct current loop control circuit controls the power switch of the soft switching inverter circuit, so that the power switch is switched on at zero voltage and switched off at zero current, and the switching loss is low; the direct current loop control circuit also needs to sample output voltage, output current, inversion current and other electrical signals in real time and send the electrical signals to microprocessors such as ARM, DSP, FPGA and the like to realize various algorithm functions.
The further optimization scheme is that the power loop comprises: the three-phase EMI filter circuit, the controllable rectifying circuit, the soft switch inverter circuit, the power transformer, the high-frequency rectifying filter circuit and the control circuit;
three-phase alternating current is denoised by a three-phase EMI filter circuit and then is input into a controllable rectifying circuit to be rectified to obtain direct current, the direct current is output after sequentially passing through a soft switch inverter circuit, a power transformer and a high-frequency rectifying and filtering circuit, the negative output end of the high-frequency rectifying and filtering circuit is used as the negative output end of a high-power torch power supply, and the positive output end of the high-frequency rectifying and filtering circuit is connected with the negative output end of a direct-current loop high-frequency rectifying and filtering circuit;
the control circuit is respectively connected with the controllable rectifying circuit, the soft switch inverter circuit and the high-frequency rectifying and filtering circuit.
The three-phase EMI filter circuit is used for denoising and resisting interference on three-phase alternating current at the power grid side and providing alternating current input for the controllable rectifying circuit; the controllable rectifying circuit converts three-phase alternating current into direct current, and the direct current is respectively input into the soft switching inverter circuit and the direct current loop soft switching inverter circuit of the controllable direct current power loop;
the three-phase EMI filter circuit is further optimized to be composed of an X capacitor, a Y capacitor, a differential mode filter inductor, a common mode filter inductor, a piezoresistor and a thermistor.
The controllable rectifying circuit is preferably a three-phase three-wire three-level VIENNA rectifying circuit or a three-phase six-switch PFC circuit so as to reduce the harmonic content at the side of the power grid and improve the power factor.
The soft switch inverter circuit inverts the received direct current into high frequency and then outputs the high frequency in a bipolar manner to provide high frequency alternating current input for the power transformer; the soft-switching inverter circuit is preferably implemented by a multi-level phase-shifted full-bridge inverter circuit, a staggered serial two-level full-bridge phase-shifted inverter circuit or a three-level full-bridge LLC inverter circuit, so that the switching loss is reduced, the efficiency is improved, and the electromagnetic interference is reduced.
The power transformer realizes electric energy isolation and level conversion and provides high-frequency alternating current input of an isolation potential for the high-frequency rectification filter circuit;
the high-frequency rectification filter circuit rectifies high-frequency alternating current input into direct current. The high-frequency rectification filter circuit is preferably realized by a synchronous rectification circuit, a full-bridge rectification circuit, a full-wave rectification circuit, a half-bridge rectification current, a half-wave rectification circuit, an LC filter circuit and a capacitor filter circuit;
the control circuit controls the power switch of the soft switching inverter circuit, so that the power switch is switched on at zero voltage and is switched off at zero current, and the switching loss is low; the control circuit controls the power switch of the synchronous rectification circuit, so that the power switch is switched on at zero voltage and switched off at zero current, and the switching loss is low. The control circuit also needs to sample electric signals such as output voltage, output current, inversion current and the like in real time, and various control functions are realized through microprocessor algorithms such as ARM, DSP, FPGA and the like.
The further optimization scheme is that the number n of the power loops in the main power loop is determined according to the highest output power P of the high-power torch power supply:
n＝P/a
in the formula, a is the power provided by a power loop, and 20-80 kW is taken as a power; n is an integer.
The further optimization scheme is that the direct current loop control circuit is also used for judging the stage of the plasma and controlling the on-off of the direct current loop soft switching inverter circuit, the direct current loop high-frequency rectification filter circuit, the direct current loop chopping power switch device, the direct current loop follow current power switch device and the direct current loop through power switch device group according to the stage of the plasma.
In a further optimization scheme, in a plasma generation stage, the direct-current loop chopping power switch device is switched on, and the direct-current loop follow-current power switch device and the direct-current loop through power switch device group are switched off. The switching-on of the direct current loop chopping power switching device enables the no-load voltage of the high-power torch power supply to be the series connection of the output voltage of the direct current loop and the output voltage of the main power loop, increases the no-load voltage between the cathode and the anode of the torch, and is matched with an arc switching circuit to easily generate stable plasma discharge.
In a further optimization scheme, in a plasma arc stabilizing stage, the direct-current loop chopping power switch device and the direct-current loop direct-connection power switch device group are turned off, and the direct-current loop follow current power switch device is turned on. The resistor plays a role in limiting current, the increase rate of current is inhibited, the plasma load is quickly and slowly established, and cathode ablation is avoided.
In the plasma continuous discharge stage, the direct-current loop chopping power switch device and the direct-current loop follow current power switch device are turned off, and the direct-current loop direct-connection power switch device group is turned on. When the direct current loop chopping power switch device is not conducted, the direct current loop follow current power switch device and the direct current loop current-limiting resistor generate power heat loss when large current passes through the direct current loop follow current power switch device and the direct current loop current-limiting resistor.
The plasma power source device is characterized in that a direct-current loop chopping power switch device is connected before process change when the plasma is possibly in a period of minactization due to discharge condition change, the output voltage of a direct-current loop soft switch inverter circuit is adjusted through high-speed current collection, the voltage between a cathode and an anode of a torch is changed, the output current is kept constant through an algorithm, and the effect of replacing a power inductor is achieved.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the high-power torch power supply applied to the plasma is improved based on the existing high-power torch power supply, the controllable direct-current power loop is additionally arranged, the controllable direct-current power loop is matched with the main power loop to adapt to different stages of plasma production, and the main power loop is connected with the direct-current power loop in series at the plasma generation stage, so that no-load voltage is improved, redundancy of a plurality of power loops is avoided, and the application range of the high-power torch power supply is expanded; in the plasma arc stabilizing stage, the high no-load voltage is beneficial to quickly establishing an arc, and the increase rate of the current is inhibited by utilizing a direct-current power loop; and in the plasma discharge stabilization stage, the direct current power loop realizes low-loss conduction. In the plasma minactization stage, large-volume devices such as a power inductor and the like are prevented from being added to a power loop, and the output current is kept constant through an algorithm, so that the effect of replacing the power inductor is achieved. The load adaptability, the volume and the weight, the output dynamic characteristics and the like of the power supply of the high-power torch are improved through different actions of different stages.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort. In the drawings:
FIG. 1 is a schematic diagram of a power supply principle of a high power torch applied to plasma;
FIG. 2 is a schematic diagram of the power supply operation of the high power torch during the plasma generation stage;
FIG. 3 is a schematic diagram of the operation of the power supply of the high power torch at the arc stabilizing stage of the plasma;
fig. 4 is a power supply operating schematic diagram of a high power torch during a plasma sustaining stage.
Reference numbers and corresponding part names in the figures:
the power supply comprises a 1-three-phase EMI filter circuit, a 2-controllable rectifying circuit, a 3-soft switching inverter circuit, a 4-power transformer, a 5-high-frequency rectifying filter circuit, a 6-control circuit, a 7-power loop, an 8-direct current loop soft switching inverter circuit, a 9-direct current loop power transformer, a 10-direct current loop high-frequency rectifying filter circuit, an 11-direct current loop chopping power switch device, a 12-direct current loop follow current power switch device, a 13-direct current loop current limiting resistor, a 14-direct current loop through power switch device group, a 15-direct current loop control circuit and a 16-controllable direct current power loop.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1
The present embodiment provides a high power torch power supply for plasma applications, as shown in fig. 1, comprising a controllable dc power loop 16 and a plurality of power loops 7; the plurality of power loops 7 are connected in parallel to form a main power loop, and the controllable direct-current power loop 16 is connected in series with the main power loop;
in the plasma generation stage, the controllable direct current power loop 16 and the main power loop are connected in series and superposed to form no-load voltage, and the no-load voltage is used for adapting to different torch devices and torch processes to generate plasma discharge;
in the plasma arc stabilizing stage, the controllable direct current power loop 16 is connected with the plurality of power loops 7 in series to improve the no-load voltage, which is beneficial to rapidly stabilizing the arc and inhibiting the increasing rate of the current;
in the plasma maintaining stage, the controllable dc power circuit 16 passes through the dc circuit direct power switch device group 14 to reduce the conduction voltage drop to be almost short-circuited, thereby reducing the heat loss;
in the plasma minactization stage, the controllable direct current power circuit 16 is connected in series with the plurality of power circuits 7 to play a role of power inductance, and the effect of larger inductance can be equivalent through algorithm presetting.
The controllable dc power loop 16 comprises: the direct current circuit soft switch inverter circuit 8, the direct current circuit power transformer 9, the direct current circuit high-frequency rectification filter circuit 10, the direct current circuit chopping power switch device 11, the direct current circuit follow current power switch device 12, the direct current circuit current-limiting resistor 13, the direct current circuit straight-through power switch device group 14 and the direct current circuit control circuit 15;
the direct current power required by the direct current loop soft switching inverter circuit 8 can be provided by a controllable rectifying circuit 2 of a certain power loop, and can also be provided by using three-phase power of a power grid after AC-DC rectification. In this embodiment, the dc power required by the dc loop soft switching inverter circuit 8 is provided by the controllable rectifier circuit 2.
The direct current power required by the direct current loop soft switch inverter circuit 8 is output after passing through the soft switch inverter circuit 8, the direct current loop power transformer 9 and the direct current loop high-frequency rectification filter circuit 10, the positive electrode output end of the direct current loop high-frequency rectification filter circuit 10 is connected with the direct current loop chopping power switch device 11 in series to serve as the positive electrode output end of the high-power torch power supply, and the negative electrode output end of the direct current loop high-frequency rectification filter circuit 10 is connected with the positive electrode output ends of the power loops 7; after the direct current loop follow current power switch device 13 is connected with the direct current loop current limiting resistor 13 in series, one end of the direct current loop follow current power switch device is connected with the positive output end of the high-power torch power supply, and the other end of the direct current loop follow current power switch device is connected with the negative output end of the direct current loop high-frequency rectifying and filtering circuit 10; one end of the direct current loop through power switch device group 14 is connected with the positive output end of the high-power torch power supply, and the other end is connected with the negative output end of the direct current loop high-frequency rectification filter circuit 10;
the direct current loop control circuit 15 is respectively connected with the direct current loop soft switching inverter circuit 8, the direct current loop high-frequency rectifying and filtering circuit 10, the direct current loop chopping power switch device 11, the direct current loop follow current power switch device 12 and the direct current loop through power switch device group 14.
The DC loop soft switch inverter circuit 8 inverts the received DC into high-frequency bipolar output and provides high-frequency AC input for a DC loop power transformer 9; the direct current loop power transformer 9 realizes electric energy isolation and level conversion; the materials adopted by the direct current loop power transformer 9 are the same as those of the power transformer 4; the high-frequency alternating current input of the direct current loop high-frequency rectifying and filtering circuit 10 is rectified into direct current with isolated potential, and a circuit adopted by the direct current loop high-frequency rectifying and filtering circuit 10 is the same as the high-frequency rectifying and filtering circuit 5;
the direct-current loop chopping power switch device 11 controls whether the potential difference of the direct-current loop is superposed on the positive potential of the power loop 7, when the driving circuit of the direct-current loop chopping power switch device 11 is low, the direct-current loop chopping power switch device 11 is not conducted, and at the moment, the potential difference of the direct-current power loop 16 is not superposed on the positive potential of the power loop 7; when the driving circuit of the dc loop chopping power switching device 11 is high, the dc loop chopping power switching device 11 is turned on, and at this time, the potential difference of the dc power loop 16 is superimposed on the positive potential of the power loop 7.
At the stage of generating plasma by high-voltage triggering excitation, the direct-current loop chopping power switch device 11 is conducted, and the direct-current power loop 16 is ensured to have larger potential difference through the change of the pulse width or the pulse frequency of the direct-current loop soft switch inverter circuit 8, so that the voltage between the cathode and the anode is increased, and stable plasma discharge is easily generated by matching with the arc-turning circuit.
In the plasma arc stabilizing stage and the plasma continuous discharge stage (i.e., the stage when the plasma is in a stable discharge condition), the dc loop chopper power switch device 11 is not turned on.
At the stage when the plasma is in the discharge condition change, the change of the pulse width or the pulse frequency of the direct current loop soft switch inverter circuit 8 ensures that the direct current power loop 16 has a smaller potential difference, and the magnitude of the potential difference can be preset through a controller algorithm or set through a user terminal. The potential difference increases the output voltage, maintaining the output current constant.
The dc loop chopping power switch device 11 adopts devices such as MOSFET, IGBT, siC, etc., and the selected principle is related to the maximum output current and the maximum output voltage of the dc power loop 16.
The DC loop follow current power switch device 12, the DC loop chopping power switch device 11 and the DC loop current limiting resistor 13 form a power topology similar to a Buck circuit. The drive circuit of the dc loop freewheeling power switch device 12 is low and the dc loop freewheeling power switch device 12 is non-conductive. The freewheeling power switch 12 drives the circuit high and the dc loop freewheeling power switch 12 is on. The dc loop freewheel power switch device 12 may provide a freewheel path at the instant the dc loop chopper power switch device 11 is turned off.
In the stage of generating plasma by high-voltage trigger excitation, the direct current loop freewheeling power switch device 12 is not conducted.
In the plasma arc stabilizing stage, the follow current power switch device 12 of the direct current loop is conducted, and the follow current power switch device 12 of the direct current loop is connected with the current limiting resistor 13 of the direct current loop in series, so that the effect of limiting the rapid change of the plasma impedance can be achieved.
The dc loop freewheeling power switch device 12 is not turned on when the plasma is in a stable discharge condition or when the plasma is in a variable discharge condition.
The follow current power switch device 12 of the dc circuit can adopt MOSFET, IGBT, siC, etc., and the selected principle is related to the maximum output current and the maximum output voltage of the dc power circuit 16.
The reverse parallel body diode is arranged in the direct current loop follow current power switch device 12, but through the on resistance with proper type selection, the tube voltage drop can be reduced through the on of the control device, and the effect of reducing the power consumption is achieved.
The current limiting resistor 13 of the direct current loop is connected with the follow current power switch device 12 of the direct current loop in series in the plasma arc stabilizing stage, the increasing rate of current is inhibited in the plasma arc stabilizing stage, and the effect of quickly and slowly establishing a plasma load is achieved.
Whether the positive output potential of the direct-current loop through power switch device group 14 is the same as the positive output potential of the power loop 7 or not, and the working states of the direct-current loop through power switch device group 14 and the direct-current loop chopping power switch device 11 are mutually exclusive.
The direct current loop direct connection power switch device group 14 adopts back-to-back MOSFETs, sic, direct current contactors and other devices to form a bidirectional switch; the dc loop pass-through power switch device group 14 is turned on at the stage of plasma arc stabilization and at the stage of plasma in a stable discharge condition, so as to avoid power heat loss generated when the dc loop chopping power switch device is turned off and the dc loop follow current power switch device and the dc loop current limiting resistor pass large current. When the back-to-back MOSFET and the Sic device are adopted to form the bidirectional switch, the bidirectional switch has the advantages of high switching speed, rich control algorithm and the like; when the bidirectional switch is formed by the direct current contactor device, the bidirectional switch has the advantages of low on-resistance, low cost, suitability for large current and the like.
The main functions implemented by the dc loop control circuit 15 are: sampling analog quantities such as output voltage, output current, inverter current and the like, collecting current of a power device, protecting, realizing driving signals of PWM or PFM, communicating with the control circuit 6 and the like. The direct current loop control circuit 15 outputs the power device drive of the direct current loop soft switching inverter circuit 8, the direct current loop high-frequency rectification filter circuit 10, the direct current loop chopping power switch device 11, the direct current loop follow current power switch device 12 and the direct current loop through power switch device group 14.
The power circuit 7 includes: the three-phase EMI filter circuit comprises a three-phase EMI filter circuit 1, a controllable rectifying circuit 2, a soft switching inverter circuit 3, a power transformer 4, a high-frequency rectifying filter circuit 5 and a control circuit 6;
the three-phase alternating current is subjected to noise removal through a three-phase EMI filter circuit 1, then bipolar input is carried out on a controllable rectifying circuit 2 for rectification to obtain bipolar direct current, the bipolar direct current is output after sequentially passing through a soft switch inverter circuit 3, a power transformer 4 and a high-frequency rectifying and filtering circuit 5, the negative output end of the high-frequency rectifying and filtering circuit 5 is used as the negative output end of a high-power torch power supply, and the positive output end of the high-frequency rectifying and filtering circuit 5 is connected with the negative output end of a direct-current loop high-frequency rectifying and filtering circuit 10;
the control circuit 6 is respectively connected with the controllable rectification circuit 2, the soft switch inverter circuit 3 and the high-frequency rectification filter circuit 5.
In this embodiment, the three-phase EMI filter circuit 1 is used to perform noise removal and interference rejection on three-phase ac power at the power grid side, and provide ac input for the controllable rectifier circuit. The three-phase EMI filter circuit 1 is composed of an X capacitor, a Y capacitor, a differential mode filter inductor, a common mode filter inductor, a piezoresistor and a thermistor, and obviously inhibits electromagnetic common mode noise and differential mode noise.
The controllable rectification circuit 2 is composed of a plurality of diodes and a plurality of power switches to form a rectification topology, and is used for converting three-phase alternating current into direct current and inputting the direct current into the soft switch inverter circuit. The controllable rectifying circuit 2 can reduce the harmonic content at the side of the power grid and improve the power factor; in this embodiment, the controllable rectifying circuit 2 may be implemented by a three-level VIENNA rectifying circuit or a three-phase six-switch PFC circuit.
The soft switch inverter circuit 3 inverts the received direct current into high-frequency bipolar and outputs the high-frequency bipolar to the power transformer 4; the soft switching inverter circuit 3 is realized by adopting a multi-level translation phase full-bridge inverter circuit, a staggered serial two-level full-bridge phase-shifting inverter circuit or a three-level full-bridge LLC inverter circuit, so that the switching loss can be reduced, the efficiency can be improved, and the electromagnetic interference can be reduced.
The power transformer 4 realizes electric energy isolation and level conversion; the magnetic core of the power transformer 4 is made of ferrite, amorphous, nanocrystalline and the like, and the coil of the power transformer 4 is made of high-frequency wire, copper foil and the like.
The high-frequency rectifying filter circuit 5 rectifies the high-frequency ac input into dc at an isolation potential. The high-frequency rectifying and filtering circuit 5 is realized by a synchronous rectifying circuit, a full-bridge rectifying circuit, a full-wave rectifying circuit, a half-bridge rectifying current, a half-wave rectifying circuit, an LC filtering circuit and a capacitor filtering circuit.
The main functions implemented by the control circuit 6 are: sampling analog quantities such as output voltage, output current, inverter current and the like, collecting current of a power device, protecting, and realizing functions such as PWM or PFM driving signals, upper computer communication, interface display and the like. The control circuit 6 outputs the power device drive of the soft switch inverter circuit 3 and the high-frequency rectification filter circuit 5.
The number n of the power loops in the main power loop is determined according to the highest output power P of the power supply of the high-power torch:
n＝P/a
wherein a is the power quantity provided by a power loop, and a is 20-80 kW.
Example 2
Based on embodiment 1, in a plasma generation stage, in this embodiment, the dc loop chopping power switch device is turned on, and the dc loop freewheeling power switch device and the dc loop pass-through power switch device group are turned off. The working circuit of the power supply of the high-power torch is shown in figure 2:
in the stage of generating plasma by high-voltage triggering excitation, the output negative potential of the direct-current power loop 16 is superposed on the output positive potential of the power loop 7, the high-power plasma torch power supply is matched with the high-voltage triggering excitation, and the arc-rotating circuit is pressed by high idle load electricity, so that stable plasma discharge is easily generated. When the dc loop control circuit 15 detects that the voltage of the high power plasma torch device drops to the arc voltage, the current rises and lasts for hundreds of milliseconds, the high voltage triggers the excitation to generate plasma, and the plasma generation phase is finished.
Example 3
Based on embodiment 1, in the plasma arc stabilization phase, in this embodiment, the dc loop chopper power switch device and the dc loop pass-through power switch device group are turned off, and the dc loop freewheel power switch device is turned on. The working circuit of the power supply of the high-power torch is shown in figure 3:
in the plasma arc stabilizing stage, the impedance changes rapidly, and the load connected in parallel with the plurality of power loops is suddenly changed from infinity to the plasma impedance, for example, the impedance is about 0.4 ohm in the argon atmosphere. If the current is very large instantaneously, short-circuit protection and device turn-off can occur, and the stable work can not be realized. If the current is not limited, the cathode ablation may be caused by a very large current. At this time, the direct current power circuit 16 controls the direct current circuit chopping power switch device 11 to be non-conductive, the direct current circuit freewheeling power switch device 12 to be conductive, and the direct current circuit straight-through power switch device group 14 to be non-conductive, so that the effect of inhibiting the increase of current can be realized, and the soft start of the rising edge can be realized. When the direct current loop control circuit 15 detects that the high-power plasma torch device rises to a preset value and is stable for hundreds of milliseconds, the plasma arc is determined to be stable, and the plasma arc stabilizing stage is finished.
Example 4
Based on embodiment 1, in the plasma sustaining stage, the dc loop chopping power switch device and the dc loop freewheeling power switch device are turned off, and the dc loop shoot-through power switch device group is turned on in this embodiment. The working circuit of the power supply of the high-power torch is shown in figure 4:
at the stage that the plasma is in a stable discharge condition, the direct-current loop direct-connection power switch device group 14 adopts back-to-back MOSFETs, IGBTs, sics, direct-current contactors and other devices to form a bidirectional switch, and at the moment, a plurality of power loops 7 are connected in parallel to supply power for the plasma torch device; with the development and progress of power devices, when the voltage drop of a direct current loop is less than 300V, the selectable low-on-resistance MOSFET is used as a back-to-back power device, and when the voltage drop of the direct current loop is more than 300V, the selectable low-on-resistance SiC is used as a back-to-back power device. When the bidirectional switch is formed by the direct current contactor device, the on-resistance is low, the cost is low, the bidirectional switch is more suitable for large current, but the response speed is slow, and a good effect can be achieved only in a certain process step. The direct current loop control circuit 15 controls the direct current loop chopping power switch device 11 to be non-conductive, controls the direct current loop follow current power switch device 12 to be non-conductive, and controls the direct current loop straight-through power switch device group 14 to be conductive; when the dc loop control circuit 15 detects that the power supply process of the high power torch is about to be finished and the load voltage and current change is severe, the plasma is at the end of the stage where the discharge condition is stable.
Example 5
Based on embodiment 1, in this embodiment, when discharge conditions change and the plasma may be in a period of minactization, the dc loop control circuit 15 determines whether to execute the following algorithm on a microsecond level:
the direct current loop control circuit 15 controls the direct current loop chopping power switch device 11 to be conducted, controls the direct current loop freewheeling power switch device 12 to be not conducted, and controls the direct current loop straight-through power switch device group 14 to be not conducted. At this time, the dc power loop 16 increases the output voltage, maintains the output current constant, and stabilizes the power output of the high power torch. The dc loop control circuit 15 can simulate the inductance effect of different inductance values by acquiring microsecond-level electrical parameters and presetting adjustable dc power loop output voltage. . When the dc loop control circuit 15 detects that the output of the high-power plasma torch device is stable, the plasma enters the stage where the discharge condition is stable again. The working circuit of the power supply of the high-power torch is shown in figure 2
The direct current loop control circuit is also used for judging the stage of the plasma and controlling the on-off of the direct current loop soft switching inverter circuit, the direct current loop high-frequency rectifying and filtering circuit, the direct current loop chopping power switch device, the direct current loop follow current power switch device and the direct current loop direct connection power switch device group according to the stage of the plasma.
The control circuit is also used for judging the stage of the plasma and controlling the controllable rectifying circuit, the soft switch inverter circuit and the high-frequency rectifying filter circuit according to the stage of the plasma.
The three-phase EMI filter circuit is composed of an X capacitor, a Y capacitor, a differential mode filter inductor, a common mode filter inductor, a piezoresistor and a thermistor.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A high power torch power supply for use in a plasma, the high power torch power supply comprising a controllable direct current power loop and a plurality of power loops; the plurality of power loops are connected in parallel to form a main power loop, and the controllable direct current power loop is connected in series with the main power loop;
in the plasma generating stage, the controllable direct current power loop and the power loop jointly generate no-load voltage for generating plasma discharge;
in the plasma arc stabilizing stage, the controllable direct-current power loop is used for inhibiting the increasing rate of the current of the main power loop;
in the plasma maintaining stage, the controllable direct current power loop is conducted;
during the plasma minactization phase, the dc power loop is equivalent to a power inductor.
2. A high power torch power supply for plasma applications as claimed in claim 1 wherein said controllable dc power loop comprises: the direct current loop soft switch inverter circuit, the direct current loop power transformer, the direct current loop high-frequency rectification filter circuit, the direct current loop chopping power switch device, the direct current loop follow current power switch device, the direct current loop current-limiting resistor, the direct current loop direct-connection power switch device group and the direct current loop control circuit;
the main power loop provides rectified bipolar direct current for the controllable direct current power loop, the bipolar direct current is output after sequentially passing through the direct current loop soft switch inverter circuit, the direct current loop power transformer and the direct current loop high-frequency rectification filter circuit, the positive output end of the direct current loop high-frequency rectification filter circuit is connected with the direct current loop chopping power switch device in series to serve as the positive output end of the high-power torch power supply, and the negative output end of the direct current loop high-frequency rectification filter circuit is connected with the main power loop; after the direct current loop follow current power switch device is connected with the direct current loop current limiting resistor in series, one end of the direct current loop follow current power switch device is connected with the positive output end of the high-power torch power supply, and the other end of the direct current loop follow current power switch device is connected with the negative output end of the direct current loop high-frequency rectifying and filtering circuit; one end of the direct current loop direct connection power switch device group is connected with the positive output end of the high-power torch power supply, and the other end of the direct current loop direct connection power switch device group is connected with the negative output end of the direct current loop high-frequency rectifying and filtering circuit;
the direct current loop control circuit is respectively connected with the direct current loop soft switch inverter circuit, the direct current loop high-frequency rectification filter circuit, the direct current loop chopping power switch device, the direct current loop follow current power switch device and the direct current loop through power switch device group.
3. A high power torch power supply for plasma applications as claimed in claim 2 wherein said power loop comprises: the three-phase EMI filter circuit, the controllable rectifying circuit, the soft switch inverter circuit, the power transformer, the high-frequency rectifying filter circuit and the control circuit;
the three-phase alternating current is subjected to noise removal through a three-phase EMI filter circuit, then bipolar input is carried out on a controllable rectifying circuit for rectification to obtain bipolar direct current, the bipolar direct current is output after sequentially passing through a soft switch inverter circuit, a power transformer and a high-frequency rectifying and filtering circuit, the negative output end of the high-frequency rectifying and filtering circuit is used as the negative output end of a high-power torch power supply, and the positive output end of the high-frequency rectifying and filtering circuit is connected with the negative output end of a direct-current loop high-frequency rectifying and filtering circuit;
the control circuit is respectively connected with the controllable rectifying circuit, the soft switch inverter circuit and the high-frequency rectifying and filtering circuit.
4. A high power torch power supply for plasma applications as claimed in claim 3 wherein the number of power loops n in the main power loop is determined according to the maximum output power P of the high power torch power supply:
n＝P/a
in the formula, a is the power quantity provided by one power loop, and a is 20-80 kW.
5. The high power torch power supply of claim 3 wherein during the plasma generation phase the DC loop chopping power switch device is on and the DC loop freewheeling power switch device and the DC loop pass-through power switch device set are off.
6. The power supply for the high power torch in the plasma body of claim 3, wherein in the arc stabilizing period of the plasma body, the DC loop chopping power switch device and the DC loop straight-through power switch device group are turned off, and the DC loop freewheeling power switch device is turned on.
7. The high power torch power supply of claim 3 wherein the DC loop chopping power switch and the DC loop freewheeling power switch are off and the DC loop pass through power switch set is on during the plasma sustaining phase.
8. The high-power torch power supply applied to the plasma as claimed in claim 2, wherein the dc loop control circuit is further configured to determine a stage of the plasma, and control the on/off of the dc loop soft switching inverter circuit, the dc loop high-frequency rectifying and filtering circuit, the dc loop chopping power switching device, the dc loop freewheeling power switching device and the dc loop pass-through power switching device group according to the stage of the plasma.
9. The power supply of the high-power torch for the plasma as claimed in claim 3, wherein the control circuit is further used for judging the stage of the plasma and controlling the controllable rectifying circuit, the soft switching inverter circuit and the high-frequency rectifying and filtering circuit according to the stage of the plasma.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211481459.9A CN115864847A (en) | 2022-11-24 | 2022-11-24 | High-power torch power supply applied to plasma |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211481459.9A CN115864847A (en) | 2022-11-24 | 2022-11-24 | High-power torch power supply applied to plasma |
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| Publication Number | Publication Date |
|---|---|
| CN115864847A true CN115864847A (en) | 2023-03-28 |
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|---|---|---|---|
| CN202211481459.9A Pending CN115864847A (en) | 2022-11-24 | 2022-11-24 | High-power torch power supply applied to plasma |
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| Country | Link |
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| CN (1) | CN115864847A (en) |
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2022
- 2022-11-24 CN CN202211481459.9A patent/CN115864847A/en active Pending
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