CN106026702A - High-power direct current plasma power supply - Google Patents

Abstract

The invention relates to a high-power direct current plasma power supply. The high-power direct current plasma power supply comprises n groups of series-wound PSM modules, a wave-smoothing inductor, a first current measurement module and a feedback control protection system, wherein the network voltage is connected with the input end of a rectifier transformer through a vacuum circuit breaker; the output end of the rectifier transformer is connected to the input ends of each group of PSM modules separately; the outputs of the n groups of series-wound PSM modules are connected to an output electrode through the wave-smoothing inductor; the first current measurement module is mounted on a major loop bus; and the input end of the feedback protection control system is connected with the first current measurement module while the output end of the feedback protection control system is connected with the control ends of the PSM modules separately. The high-power direct current plasma power supply has a large power supply output voltage range; the output power can achieve the MW level; and meanwhile, the high-power direct current plasma power supply has good dynamic characteristics, quite short reaction time, and good current control characteristics, and can rapidly response to the sharp disturbance of the plasma load and can ensure the quality of the plasmas products.

Description

A High Power DC Plasma Power Supply

technical field

The invention relates to a power supply, in particular to a high-power DC plasma power supply.

Background technique

At present, plasma technology is more and more widely used in metallurgy, spraying, surface modification, environmental treatment, communication and detection, and other industrial fields. Plasma chemical industry is clean and pollution-free in the production process, and does not require the use of catalysts. Simple, wide adaptability of raw materials, in today's shortage of resources and increasingly severe environmental problems, how to use plasma technology efficiently and rationally is a major issue related to environmental protection, comprehensive utilization of resources, energy saving and emission reduction, and industrial structure optimization. However, to realize multiple applications and comprehensive promotion of plasma technology, the key is to have a high-power plasma power supply with fast response, good control performance, and high reliability and a high-performance plasma generator.

According to the arc theory and the plasma process, the energy stability of the plasma load is directly related to the current, and the plasma power supply mainly adopts a constant current source. During the process, due to the comprehensive influence of various factors such as gas discharge characteristics, gas pressure, gas components, and plasma temperature, the plasma load will be greatly disturbed, such as arcing, which will cause a sharp decrease in the plasma load resistance. Small, the output of the plasma power supply is approximately short-circuited, so the plasma load generally exhibits a level or rising volt-ampere characteristic. If the output voltage of the plasma power supply cannot quickly respond to the change of the load impedance, it will be difficult to stabilize the output current, thereby losing the process conditions of the plasma, unable to maintain the normal discharge process, and thus unable to guarantee the process effect and affecting product quality. Therefore, the plasma power supply must have steep drop characteristics, must have good dynamic characteristics, and a short response time to adapt to sharp changes in load.

For a long time, traditional high-power plasma DC power supplies at home and abroad have generally used silicon-controlled rectifier power supplies. In order to obtain the required steep drop characteristics and stable operating current, it is usually necessary to add a vacuum adjustment tube in the circuit, or to connect energy consumption in series. Due to the frequency of the AC circuit and the characteristics of the thyristor rectifier circuit, the response time of the thyristor rectifier power supply can only reach the millisecond level (such as three-phase bridge rectifier under power frequency The average out-of-control time of the circuit reaches 1.27ms), and the power factor of the thyristor rectifier power supply is not high. Therefore, this kind of power supply is not only low in efficiency and high in energy consumption, but also bulky, heavy, slow in dynamic response, poor in control performance, and difficult to adapt to sharp changes in load impedance characteristics.

In recent years, plasma power supplies made using high-frequency full-bridge inverter technology have also appeared. Compared with traditional thyristor rectifier power supplies, although high-frequency inverter power supplies have energy-saving, material-saving, small impact on the power grid, and better control performance, etc. However, in the working environment of high-power plasma loads, high-power inverter plasma power supplies have strong energy efficient transfer and reliability caused by factors such as parallel current sharing, temperature rise, electromagnetic interference, complex structure, and parasitic parameters. question.

The research and development of high-performance and high-reliability high-power DC plasma power supply is the bottleneck of the development of high-power plasma systems at home and abroad, and plays a vital role in the overall development and popularization of high-power plasma systems.

Contents of the invention

The purpose of the present invention is to provide a high-power DC plasma power supply, which not only has good dynamic performance, can quickly respond to sharp changes in the output impedance of the plasma load within a few microseconds, stabilize the output current, and ensure product quality, but also has High power factor, high efficiency and reliability.

In order to achieve the above object, the present invention adopts the following technical solutions: including n groups of series-connected PSM modules, smoothing inductors, the first current measurement module and a feedback control protection system, the grid voltage is connected to the input end of the rectifier transformer through a vacuum circuit breaker, The output terminals of the rectifier transformer are respectively connected to the input terminals of each group of PSM modules, and the outputs of n groups of series-connected PSM modules are connected to the output electrodes through smoothing inductors, and the first current measurement module is installed on the main circuit bus for measuring The output current of the power supply is converted into a voltage output in proportion and then connected to the feedback control protection system. The input terminal of the feedback protection system is connected to the first current measurement module, and its output terminals are respectively connected to the control terminals of the PSM module.

As a further improvement of the above technical solution:

The feedback control protection system includes a digital controller and a parameter setting operation state monitoring unit, the parameter setting operation state monitoring unit is interactively connected with the digital controller, and the output end of the digital controller is connected to each PSM module through an optical fiber The control terminal is connected;

The feedback control and protection system is used for real-time communication with the parameter setting operation state monitoring unit, and simultaneously detecting the output of the current measurement module on the main circuit, and calculating the number of PSM modules that need to be switched.

The PSM module includes an isolation transformer, a vacuum contactor, a soft charging resistor, a rectifier circuit, a freewheeling diode, a varistor, an insulated gate bipolar transistor, an IGBT drive and control module, a comparator and a second current measurement module; The rectification circuit is composed of six power diodes, the AC input terminals of the rectification circuit are respectively connected to the primary side of the isolation transformer through an AC fuse and a vacuum contactor in turn, and the soft charging resistor is connected in parallel at both ends of the vacuum contactor , the negative output end of the rectifier circuit is connected to the collector of the insulated gate bipolar transistor, the emitter of the insulated gate bipolar transistor is connected to the cathode of the freewheeling diode, and the gate and collector of the insulated gate bipolar transistor The emitter is connected to the output terminal of the IGBT drive and control module, the anode of the freewheeling diode is connected to the positive output terminal of the rectifier circuit, and the anode of the freewheeling diode is connected to the collector of the insulated gate bipolar transistor through the absorption capacitor, The piezoresistor, output resistor and filter capacitor are respectively connected in parallel at the output terminal of the rectifier circuit, the second current measurement module is installed at the emitter of the insulated gate bipolar transistor, and the positive input terminal of the comparator is connected via a low The pass filter is connected to the second current measurement module, its reverse input terminal is connected to the power supply VCC through the peripheral circuit, the output terminal of the comparator is connected to the input terminal of the IGBT drive and control module, and the power supply terminal of the IGBT drive and control module Connect to the secondary side of the isolation transformer.

The PSM module also includes an indicating circuit, the indicating circuit is composed of a current-limiting resistor and a light-emitting diode, the cathode of the light-emitting diode is connected to the positive output terminal of the rectifier circuit, and its anode is connected to the insulating barrier double through the current-limiting resistor. The emitter of the polar transistor is connected.

It can be seen from the above technical solution that the high-power DC plasma power supply of the present invention has a large output voltage range, and the output power can reach MW level, has good dynamic characteristics, very short response time, and can respond quickly (micro Second level) large disturbance of plasma load, with good current control characteristics, to ensure the quality of plasma products. The high-power DC plasma power supply has a simple structure and has a fault redundancy function. The failure of some modules will not affect the normal operation of the power supply and has high reliability. cost.

Description of drawings

Fig. 1 is an overall circuit diagram of the present invention;

Fig. 2 is a schematic circuit diagram of the PSM module in the present invention.

detailed description

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, the high-power DC plasma power supply of this embodiment includes n groups of PSM modules 2 connected in series, a smoothing inductor 7, a first current measurement module 8 and a feedback control and protection system, and the grid voltage passes through a vacuum circuit breaker 1 It is connected to the input terminal of the rectifier transformer 3, and the output terminal of the rectifier transformer 3 is respectively connected to the input terminal of each group of PSM modules 2, and the output of n groups of series-connected PSM modules 2 is connected to the output electrode through the smoothing inductor 7, and the first current measurement The module 8 is installed on the main circuit bus to measure the output current of the power supply, and convert it into a voltage output in proportion and then connect it to the feedback control and protection system. The input terminal of the feedback protection system is connected to the first current measurement module 8, and its output terminals are respectively Connect to the control terminal of PSM module 2.

The feedback control protection system includes a digital controller 9 and a parameter setting operation state monitoring unit 10, the parameter setting operation state monitoring unit 10 is interactively connected with the digital controller 9, and the output end of the digital controller 9 is connected to each PSM through an optical fiber 11 The control terminal of the module 2 is connected; the feedback control protection system is used for real-time communication with the parameter setting operation state monitoring unit 10, and simultaneously detects the output of the current measurement module on the main circuit, and calculates the PSM module 2 required for switching. number.

As shown in Figure 2, the PSM module 2 includes an isolation transformer 34, an indicating circuit, a vacuum contactor 21, a soft charging resistor 22, a rectifier circuit 24, a freewheeling diode 31, a varistor 25, an insulated gate bipolar transistor 28, an IGBT The drive and control module 35, the comparator 37 and the second current measurement module 30; the rectification circuit 24 is composed of six power diodes, and the AC input end of the rectification circuit 24 respectively passes through the AC fuse 23, the vacuum contactor 21 and the isolation transformer 34 in sequence connected to the primary side, the soft charging resistor 22 is connected in parallel to both ends of the vacuum contactor 21, the negative output terminal of the rectifier circuit 24 is connected to the collector of the insulated gate bipolar transistor 28, and the emitter of the insulated gate bipolar transistor 28 is connected to the The cathode of the freewheeling diode 31 is connected, the grid, collector and emitter of the insulated gate bipolar transistor 28 are connected with the output terminal of the IGBT drive and control module 35, and the anode of the freewheeling diode 31 is connected with the positive output terminal of the rectifier circuit 24 The anode of the freewheeling diode 31 is connected to the collector of the insulated gate bipolar transistor 28 through the absorbing capacitor 29, the piezoresistor 25, the output resistor 26 and the filter capacitor 27 are respectively connected in parallel to the output terminal of the rectifier circuit 24, and the second current The measurement module 30 is installed on the emitter of the insulated gate bipolar transistor 28, the positive input terminal of the comparator 37 is connected to the second current measurement module 30 through the low-pass filter 36, and its negative input terminal is connected to the power supply VCC through the peripheral circuit The output end of the comparator 37 is connected to the input end of the IGBT drive and control module 35 , and the power supply end of the IGBT drive and control module 35 is connected to the secondary side of the isolation transformer 34 . The indicating circuit is composed of a current-limiting resistor 33 and a light-emitting diode 32. The cathode of the light-emitting diode 32 is connected to the positive output terminal of the rectifier circuit 24, and its anode is connected to the emitter of the IGBT 28 through the current-limiting resistor 33.

The primary side of the rectifier transformer 3 adopts a delta connection method, which can prevent the 3rd harmonic current from flowing into the power grid. The secondary side of the rectifier transformer 3 is star connection method 4 and delta connection method 5 alternately, so that 12 pulses can be finally output on the DC side The rectified voltage can reduce the ripple on the DC side and effectively suppress the waveform distortion on the AC side. After being converted into a suitable voltage by the rectifier transformer 3, it enters the input terminal of the PSM module 2. The rectifier unit and filter unit in the PSM module 2 can convert the AC voltage into a stable DC voltage. The on and off of the IGBT switch unit determines the Whether the PSM module is switched on or not, the output voltage of each group of PSM modules 2 is Um. After n groups of identical PSM modules 2 are connected in series, the maximum output voltage value can reach n*Um. The output voltage value of the power supply at any time depends on the input PSM The number of modules, its value is Uout=m*Um (among them, m is the number of input modules, m ≤ n), the output voltage of the power supply is adjustable between 0 and n*Um, when a PSM module 2 is turned off , the freewheeling diode 31 in the shutdown module provides a freewheeling channel for the current in the loop. The output of n groups of PSM modules 2 connected in series is connected to both ends of the electrodes of the plasma load through the output inductance 7. The output inductance 7 can smooth the output current and reduce the current ripple.

The feedback control and protection system of the present invention takes the digital controller 9 as the core, and through real-time communication with the parameter setting and operating state monitoring unit 10, receives the operating parameters of each power supply, and uploads the actual operating state of the power supply in real time; The first LEM current measurement module 8 measures the output current value of the power supply in real time, and converts it into a voltage output in proportion, and transmits the voltage value to the analog input port of the digital controller 9 through a shielded cable, and the digital controller 9 converts it into a corresponding The digital quantity is compared with the current setting value in the operating parameters, PID calculation, etc., and the number of PSM modules 9 required for switching is calculated, which is output by the corresponding GPIO interface of the digital controller 9 and connected through the optical fiber transmission 11 To the control and drive unit 35 of each PSM module 2, so that the insulated gate bipolar transistor 28 in the corresponding PSM module 2 can be quickly turned on or off, so as to realize the rapid change of the output voltage of the power supply, so that the output current can quickly track and stabilize At the current setting value; the optical fiber transmission unit can also transmit the working status of each PSM module 2 to the digital controller 9 in real time, and upload it to the running status monitoring system.

As shown in Figure 2, the indicating circuit that light-emitting diode 32 and current-limiting resistor 33 are connected in series is used for displaying the working status of each PSM module 2, and the second current measuring module 30 is used for monitoring the output of each PSM module 2 current. The vacuum contactor 21 and the soft charging resistor 22 form a soft charging circuit. In the preparation stage, when the vacuum circuit breaker 1 is closed and the rectifier transformer 3 is charged, the PSM module 2 charges the filter capacitor 27 through the soft charging resistor 22 and the rectifying circuit 24. When the voltage on the filter capacitor 27 reaches 70% of its peak value, then close the vacuum contactor 21, which can effectively prevent the capacitor voltage from being overcharged. At the same time, if it is found that the voltage across the filter capacitor 27 is higher than the protection threshold , can also directly break the vacuum contactor 21 to protect the safety of equipment and devices. The rectifier circuit 24 is made up of six power diodes, three of which are common anode connections, and the other three are common cathode connections, and a filter capacitor 27 is connected in parallel on the output side to form a three-phase uncontrollable rectification filter circuit together. The AC voltage is converted into a stable DC voltage; the AC fuse 23 connected in series with the three-phase AC input circuit is used to protect the interphase short-circuit overcurrent; DC side output overvoltage; the output stage of the PSM module 2 is composed of a switch unit with a buck structure topology composed of an IGBT module 28 and a fast recovery freewheeling diode 31. Whether each PSM module 2 is put into operation or not only needs to be turned on or off It can be realized by disconnecting the insulated gate bipolar transistor 28 (that is, the IGBT); the absorbing capacitor 29 connected in parallel to the collector of the IGBT and the anode of the freewheeling diode 31 uses a non-inductive capacitor, which can suppress the turn-off overvoltage of the IGBT and the freewheeling diode 31 and du/dt, to reduce switching loss and noise during turn-off; when the IGBT module 28 is turned on, the PSM module 2 is put into operation, and the light-emitting diode 32 connected to the output terminal of the module is lit, indicating that the module is in a working state. The current-limiting resistor 33 connected in series with the light-emitting diode limits the current passing through the branch of the light-emitting diode. When the IGBT module 28 is turned off, the PSM module is not put into operation, and the current in the main circuit continues to flow through the free-wheeling diode 31, and the light-emitting diode 32 is extinguished at the same time. Indicates that the PSM module 2 is not in operation.

As shown in Figure 2, the power supply of the IGBT drive and control module 35 is taken from the three-phase AC input side of the PSM module 2, and two phases of the three-phase AC input side are converted into suitable low voltage by the isolation transformer 34 and then supplied. The IGBT drive and control module is converted into DC voltages of various voltage levels inside the module to provide DC working power for different devices, which can ensure that the entire PSM module 2 has good insulation and withstand voltage levels; the PSM module 2 and the main control circuit The signal communication of the main control circuit is all carried out through the optical fiber transmission 11, and the control signal of the main control circuit is transmitted to the signal receiving end of the IGBT drive and control module 35 through the optical fiber transmission 11, and the driving circuit in the module quickly outputs positive and negative driving voltages and applies them to the gate of the IGBT and the two ends of the emitter can control the IGBT to be quickly turned on or off, and at the same time, the working state of the PSM module 2 can also be transmitted 11 to the main controller through the optical fiber. The LEM current measurement module 30 installed on the IGBT switch side output bus of each PSM module 2 is used to measure the output current of each PSM module, and after being converted into voltage output in proportion, it is filtered by a low-pass filter 36. In addition to the high-frequency interference signal, it is connected to the output terminal of the comparator 37 together with the preset overcurrent protection threshold voltage, and the output of the comparator 37 is connected to the input port of the IGBT drive and control module 35. If the output current of the PSM module exceeds the protection threshold , then the output of the comparator 37 is a high level, and the IGBT drive and control module 35 will immediately output a negative voltage to turn off the IGBT switch immediately, cut off the output of the PSM module 2, and prevent damage to equipment and devices due to overcurrent.

The power supply of the present invention is suitable for plasma loads. During the working process, due to the influence of various factors such as the discharge characteristics of the plasma load, gas pressure, and temperature, the plasma load will be violently disturbed, which requires the plasma power supply It has good dynamic characteristics and can quickly respond to sharp changes in load impedance characteristics. Adopting the topological structure of two PSM modules connected in series, and using the IGBT switch to quickly turn on and off the output of the PSM module, it can respond to the sharp change of the load voltage within a few microseconds, stabilize the current output, and at the same time, in the event of overcurrent, In the event of overvoltage and other faults, the power output can also be cut off within a few microseconds to ensure the safety of the equipment; not only that, when a certain or k PSM modules cannot work due to a fault, as long as the expected output voltage value is less than (n-k) *Um, the power supply can still continue to work, so the new high-power DC plasma power supply also has a good fault redundancy function.

The above-mentioned embodiments are only descriptions of preferred implementations of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (5)

1. A high-power DC plasma power supply, characterized in that: it includes n groups of series-connected PSM modules (2), smoothing inductors (7), a first current measurement module (8) and a feedback control and protection system. The vacuum circuit breaker (1) is connected to the input end of the rectification transformer (3), the output end of the rectification transformer (3) is respectively connected to the input end of each group of PSM modules (2), and the output of n groups of series-connected PSM modules (2) It is connected to the output electrode through the smoothing inductor (7), and the first current measurement module (8) is installed on the main circuit bus to measure the output current of the power supply, and convert it into a voltage output in proportion and then connect it to the feedback control protection system , the input end of the feedback protection system is connected to the first current measurement module (8), and the output ends thereof are respectively connected to the control end of the PSM module (2). 2. The high-power DC plasma power supply according to claim 1, characterized in that: the feedback control protection system includes a digital controller (9) and a parameter setting operation status monitoring unit (10), and the parameter setting The constant running state monitoring unit (10) is interactively connected with the digital controller (9), and the output end of the digital controller (9) is connected with the control end of each PSM module (2) through an optical fiber (11). 3. The high-power DC plasma power supply according to claim 2, characterized in that: the feedback control protection system is used for real-time communication with the parameter setting operation status monitoring unit (10), and at the same time detects the The output of the current measurement module is used to calculate the number of PSM modules (2) that need to be switched. 4. The high-power DC plasma power supply according to claim 1, characterized in that: the PSM module (2) includes an isolation transformer (34), a vacuum contactor (21), a soft charging resistor (22), a rectifier circuit (24), freewheeling diode (31), varistor (25), insulated gate bipolar transistor (28), IGBT drive and control module (35), comparator (37) and second current measurement module ( 30); the rectification circuit (24) is composed of six power diodes, and the AC input terminals of the rectification circuit (24) respectively pass through the AC fuse (23), the vacuum contactor (21) and the isolation transformer (34) The primary side of the rectification circuit (24) is connected to the collector of the insulated gate bipolar transistor (28) , the emitter of the insulated gate bipolar transistor (28) is connected to the cathode of the freewheeling diode (31), and the gate, collector and emitter of the insulated gate bipolar transistor (28) are connected to the IGBT drive and control module (35 ), the anode of the freewheeling diode (31) is connected to the positive output terminal of the rectifier circuit (24), and the anode of the freewheeling diode (31) is connected to the insulated gate bipolar transistor ( 28) connected to the collector, the piezoresistor (25), the output resistor (26) and the filter capacitor (27) are respectively connected in parallel to the output end of the rectifier circuit (24), and the second current measurement module (30) is installed At the emitter of the insulated gate bipolar transistor (28), the positive input terminal of the comparator (37) is connected to the second current measurement module (30) through a low-pass filter (36), and its negative input terminal The peripheral circuit is connected to the power supply VCC, the output terminal of the comparator (37) is connected to the input terminal of the IGBT drive and control module (35), the power supply terminal of the IGBT drive and control module (35) is connected to the isolation transformer (34) Secondary side connected. 5. The high-power DC plasma power supply according to claim 4, characterized in that: said PSM module (2) also includes an indicator circuit, said indicator circuit consists of a current limiting resistor (33) and a light emitting diode ( 32), the cathode of the light-emitting diode (32) is connected to the positive output terminal of the rectifier circuit (24), and its anode is connected to the emitter of the insulated gate bipolar transistor (28) through the current limiting resistor (33).