A method and system for high voltage and high current flat-topped pulse generation

Abstract

The present invention discloses a method and a system for high voltage and high current flat-topped pulse generation wherein a Marx Generator configured to generate the high voltage and the high current; an output switch (So) connected to the Marx Generator, and configured to discharge the high voltage generated by the Marx generator; a peaking capacitor (Cpc) connected to the output switch (So), and configured to be charged by the generated high voltage through the output switch; and a peaking switch (Spk) connected the peaking capacitor, and configured to discharge the peaking capacitor through a load to generate the flat top pulse at the load. [Figure -2]

Description

TECHNICAL FIELD

[0001] The present disclosure relates to pulse generator. The disclosure,more particularly, relates to high voltage and high current flat-topped pulsegenerator based on Marx generator.BACKGROUND

[0002] Many electrical systems such as particle beam accelerators, lasers,high power microwave systems, etc.; require nearly rectangular (flat-topped pulse)high voltage electrical pulses. These requirements are currently met with differentcircuit technique selected according to the desired pulse shape parameters andrepetition rate specifications. To generate this kind of rectangular (flat-toppedpulse) high voltage electrical pulses, conventionally pulse forming line driven byeither tesla transformer or Marx generator is used. But each of these configurationsis having its own disadvantages, when operating in repetitive mode. Both units arebulky and need more energy input for generating the required flat-topped pulse atrequired voltage and current. In another method, the Marx generator is utilizing fordriving the load, but getting flat pulse is not possible. Third method is developingpulse forming network. In which, flat pulse can be obtained but getting the requiredhigh current at high voltage nano second regime is difficult. The Marx generatorwith Pulse Forming Line (PFL) can be used for generating flat pulse but it is bulky.Also primary voltage of Marx is more and physical length of the system is larger.The Tesla transformer based compact repetitive systems also can be used forgenerating flat pulse, but increasing the pulse width, with the same compactconfiguration is not possible. The Pulse Forming Network (PFN) type Marxgenerator can be used. However, it also needs more PFN modules to achieverequired load voltage. Also, it cannot be used for generating higher current.

[0003] Ref. 1, "ADA report No.635535 JUN 1987,"A 2.5 Gigawatt liquiddielectric coaxial pulse forming line, T. L. Berger, V. H. Gehman, D. D. Lindberg"deals with the development of PFL driven by Marx generator to achieve rectangularflat pulse. In this, length of the PFL and dielectric used decide the flat pulse width.Marx generator is used to charge the PFL. In this method primary energy requiredin Marx generator is more and output voltage will be half of the Marx erectedvoltage.

[0004] Ref. 2 "Review of Scientific Instruments "Characterization andanalysis of a pulse power system based on Marx generator and Blumlein"DOI:10.1063 / 1.2813898, DP Kumar" gives the development of a different pulseforming line (PFL) called Blumeline PFL driven by Marx generator to achieverectangular flat pulse. In this, the output voltage of PFL and Marx erected voltageare same but construction of Blumeline PFL is complex and pre pulse problems arealso there.

[0005] Ref. 3 "High Power Laser and Particle Beams; v. 18(3); p. 451-454. Development of a 1.0 MV 100 Hz compact Tesla transformer with PFL. 18.451-454. Kang, Qinlan & Chang, A.-B & Li, M.-J & Meng, F.-B & Su, Y.-B. (2006)"& Ref. 4 "IEEE Transaction on plasma science. 42(10),. PP 2876-2885." . M.Novac, M. Wang, I. R. Smith and P. Senior (2014). A 10 GW Tesla-Driven BlumleinPulsed Power Generator" describe, the development of PFL (PFL) driven by Teslatransformer to achieve rectangular flat pulse. In this, length of the PFL anddielectric used in PFL is decide the flat pulse width. Tesla transformer is used tocharge the PFL and the output voltage at load will be half of the output voltage ofTesla transformer. Also, it is not possible to develop the compact tesla transformer,which makes the system bulky.

[0006] Ref. 5 "US20060290399A1", Ref. 6 "Design, construction andcharacterization of a line-type pulse modulator for driving high power magnetronSBMO / IEEE MTT-S International Conference on Microwave and Optoelectronics,2005. DOI: 10.1109 / IMOC.2005.1580011", Ref.7 "AFRL-RD-PSTP-2014-0003,"A Compact 700-kV erected pulse forming network for HPM applications",Ref.8 "IEEE Transactions on Plasma Science ( Volume: 37, Issue: 1, Jan.2009),"Development of Rectangle-Pulse Marx Generator Based on PFN"Hongtao Li; Hong-Je Ryoo; Jong-Soo Kim; Geun-Hie Rim; Young-Bae Kim;Jianjun Deng" & Ref. 9 "Laser and particle beam Volume 2021 |Article ID6686530," A High-Power Pulse Generator Based on Pulse Forming Network andLinear Transformer" Mingjia Li,1 Qiang Kang,2 Jie Tan,2 Min Luo,2 and FeiXiang2" deal with the development of pulse forming network for generating flatrectangular pulse at High Voltage. In this, obtaining rectangular pulse is possiblebut is difficult to generate required higher current at high voltage nano secondregime.

[0007] Ref. 10 "2009 IEEE Pulsed Power Conference DOI:10.1109 / PPC.2009.5386235 "Development of a sequentially switched Marx generator for HPM loads" J.R. Mayes; C.W. Hatfield" show the generation ofrectangular pulse by discharging multiple Marx generators (MG)in sequence. Thisneeds number of MG to generate a single pulse, which is very complex and so it isnot possible to develop this as a compact system.

[0008] In research work on pulsed power source, in general, a peakingcapacitor is used for reducing the rise time. However, flat pulse cannot be obtained.

[0009] There is therefore felt a need of an invention which provides asystem and method for high voltage, high current flat top pulse generator based onMarx generator. The proposed system eliminates the complexity and disadvantagesof the conventional methods.OBJECT OF THE INVENTION

[0010] The principal object of the embodiments herein is to provide asystem high voltage and high current flat-topped pulse generator based on Marxgenerator.

[0011] Another object of the embodiments herein is to provide a method forhigh voltage and high current flat-topped pulse generator based on Marx generator.

[0012] Another object of the embodiments herein is to provide a gaspurging arrangement to control Marx generator.

[0013] Another object of the embodiments herein is to achieve flat-toppedpulse of ~70 ns.SUMMARY OF THE INVETION

[0014] The present disclosure provides a technique to achieve flat pulse by designing suitable Marx erected capacitance (Cmarx), Marx series inductance(Lmarx), Peaking capacitor inductance (Lpc) and capacitance (Cpc), inductance(Lpk) and operating pressure (p2) of peaking switch of Marx generator based pulsedpower source. Using these designed value, a system was built and tested withresistive load and microwave load of fixed impedance and a flat pulse width of ~70 ns was obtained.

[0015] In one aspect, the object is satisfied by providing a system for highvoltage and high current flat-topped pulse generation, the system comprises a MarxGenerator configured to generate the high voltage and the high current; an outputswitch (So) connected to the Marx Generator, the output switch configured todischarge the high voltage generated by the Marx generator; a peaking capacitor(Cpc) connected to the output switch (So), the peaking capacitor configured to becharged by the generated high voltage through the output switch; and a peakingswitch (Spk) connected the peaking capacitor, the peaking switch configured todischarge the peaking capacitor through a load to generate the flat top pulse at theload.

[0016] In another aspect, a method for high voltage and high current flattopped pulse generation, the method comprising the steps of generating the highvoltage and the high current by configuring a Marx Generator; discharging thegenerated high voltage by configuring an output switch (So) connected to the MarxGenerator; charging a peaking capacitor (Cpc) connected to the output switch (So)by the generated high voltage through the output switch; and discharging thepeaking capacitor through a load by configuring a peaking switch (Spk) connectedthe peaking capacitor.BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0017] The detailed description is described with reference to theaccompanying figures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. The same numbersare used throughout the drawings to reference like features and modules.

[0018] Figure 1 illustrates a circuit diagram of proposed Marx generatorwithout peaking capacitor, according to an exemplary implementation of thepresent disclosure.

[0019] Figure 2 illustrates a block diagram of proposed pulse generator,according to an exemplary implementation of the present disclosure.

[0020] Figure 3 illustrates an equivalent circuit of the proposed pulsegenerator, according to an exemplary implementation of the present disclosure.

[0021] Figure 4 illustrates simulation results of output voltage with flatpulse of ~70 ns, according to an exemplary implementation of the presentdisclosure.

[0022] Figure 5 illustrates Experimental results of output voltage with flatpulse of ~70 ns, according to an exemplary implementation of the presentdisclosure.

[0023] It should be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative methods embodying theprinciples of the present disclosure. Similarly, it will be appreciated that any flowcharts, flow diagrams, and the like represent various processes which may besubstantially represented in computer readable medium and so executed by acomputer or processor, whether or not such computer or processor is explicitlyshown.DETAILED DESCRIPTION

[0024] The various embodiments of the present disclosure describe abouttechniques for high voltage and high current flat-topped pulse generator based onMarx generator.

[0025] In the following description, for purpose of explanation, specificdetails are set forth in order to provide an understanding of the present disclosure.It will be apparent, however, to one skilled in the art that the present disclosure maybe practiced without these details. One skilled in the art will recognize thatembodiments of the present disclosure, some of which are described below, may beincorporated into a number of systems.

[0026] However, the systems and methods are not limited to the specificembodiments described herein. Further, structures and devices shown in the figuresare illustrative of exemplary embodiments of the present disclosure and are meantto avoid obscuring of the present disclosure.

[0027] It should be noted that the description merely illustrates theprinciples of the present invention. It will thus be appreciated that those skilled inthe art will be able to devise various arrangements that, although not explicitlydescribed herein, embody the principles of the present invention. Furthermore, allexamples recited herein are principally intended expressly to be only forexplanatory purposes to help the reader in understanding the principles of theinvention and the concepts contributed by the inventor to furthering the art and areto be construed as being without limitation to such specifically recited examplesand conditions. Moreover, all statements herein reciting principles, aspects, andembodiments of the invention, as well as specific examples thereof, are intended toencompass equivalents thereof.

[0028] In an exemplary aspect of the present disclosure, the pulsed powersystem claimed herein consists of a Marx Generator with a rated voltage of 400kVto 600kV and current of 10 kA-15kA and pulse repetition rate from 100 Hz- 150Hz.

[0029] In one embodiment, a system for high voltage and high current flattopped pulse generation, the system comprises a Marx Generator configured togenerate the high voltage and the high current; an output switch (So) connected tothe Marx Generator, the output switch configured to discharge the high voltagegenerated by the Marx generator; a peaking capacitor (Cpc) connected to the outputswitch (So), the peaking capacitor configured to be charged by the generated highvoltage through the output switch; and a peaking switch (Spk) connected thepeaking capacitor, the peaking switch configured to discharge the peaking capacitorthrough a load to generate the flat top pulse at the load.

[0030] In another embodiment, a method for high voltage and high currentflat-topped pulse generation, the method comprising the steps of generating the highvoltage and the high current by configuring a Marx Generator; discharging thegenerated high voltage by configuring an output switch (So) connected to the MarxGenerator; charging a peaking capacitor (Cpc) connected to the output switch (So)by the generated high voltage through the output switch; and discharging thepeaking capacitor through a load by configuring a peaking switch (Spk) connectedthe peaking capacitor.

[0031] In another embodiment, the Marx Generator comprises a plurality ofstage capacitors (Cn) to generate required erected capacitance (Cmarx), wherein theplurality of stage capacitors (Cn) are interconnected with a plurality of spark-gapswitches in a way such that the plurality of stage capacitors are in parallel with acharging power supply, wherein after the charging voltages of plurality of stagecapacitors (Cn) reach the breakdown voltage of the corresponding plurality ofspark-gap switches , all the stage capacitors (Cn) are connected in series duringdischarge and generating the designed erected voltage / capacitance (Cmarx); andwherein the breakdown voltage of spark gaps is decided by a gap spacing and a gaspressure in the spark-gap switch; and a plurality of charging and ground inductors(Ln) to charge the stage capacitors (Cn), wherein the plurality of charging andground inductors (Ln) are connected in series with the plurality of stage capacitors(Cn); and during discharge, erected series inductance (Lmarx) is based on Stagecapacitors, Spark gaps and connecting leads in the discharge path of MarxGenerator.

[0032] In another embodiment, the Marx Generator can operate from 100-150Hz repetition rate at voltage and current of 400kV-600kV and 10 kA-15kA.

[0033] In another embodiment, the output switch (So) is in open conditionduring charging phase of the stage capacitors (Cn).

[0034] In another embodiment, the duration of the flat top pulse is based onCmarx to Cpc value along with Peaking switch pressure.

[0035] In another embodiment, the Cmarx to the Cpc ratio is atleast 1.5times for achieving the flat top pulse.

[0036] In another embodiment, the peaking switch (Spk) is operated in 60%to 80% of its maximum value for achieving the flat top pulse.

[0037] In an embodiment, the flat pulse width of 70 ns duration can beachieved.

[0038] In another embodiment, the plurality of spark-gap switches istriggered by a plurality of linking resistors (Rt).

[0039] In an advantageous embodiment, the flat-topped pulse is achievedby varying the pressure p1 of the peaking spark-gap switch (Spk).

[0040] Figure 1 illustrates a circuit diagram of proposed Marx Generatorwithout peaking capacitor. The MG comprises of plurality of capacitorsinterconnected through spark-gap switches in such a way that all the capacitors arein parallel with charging power supply and after the charging voltages reaches thebreakdown voltage of the spark-gap switches (decided by the gap spacing and gaspressure in the gap), the capacitors come in series and discharge through the loadconnected at the end of the Marx Generator. Thus, if there are N capacitors in theMG and each capacitor is charged to a voltage Vch, then the erected voltage of theMG would be NVch. But the actual output voltage of the MG is governed by theload connected across it. Fig.1 shows the circuit diagram of a designed MG withoutpeaking capacitor.

[0041] Pulse width of the MG is decided by the erected capacitance andtotal series inductance. Output pulse of this MG is double exponential and havinglarger rise time which cannot be used for driving intended loads. Low inductancepulse compression line (conventionally pulse forming line) is required forgenerating the required rectangular pulse and reducing the rise time. In thisproposal, low inductance peaking capacitor is used as pulse compression line. Ingeneral, peaking capacitor is used for only reducing the rise time but in this proposalit is used along with Marx generator with suitably designed parameter forgenerating flat pulse.

[0042] Figure 2 illustrates a block diagram of proposed pulse generator. Theconfiguration of HV HC MG based puled power source (PPS) is disclosed. Marxgenerator and peaking capacitor parameters are designed to meet the flat top,voltage and current requirements. The required High Voltage is generated by Marxgenerator and gas in / out used for spark gap in the Marx generator. The output switchis used for discharging the High Voltage to Peaking capacitor connected in serieswith Marx generator, also it serves as open condition during charging phase of Marxcapacitors. The Peaking capacitor is co axial High voltage capacitor. The Peakingswitch is used for closing the Output of Peaking capacitor to load. It also used gasfor its operation. The equivalent capacitance i.e. Cmarx of Marx generator and peakcapacitance i.e. Cpc value of peaking capacitor along with Peaking switch pressuredecides the output voltage value and flat top duration. Cmarx to Cpc ratio wasarrived is 1.5 times or more for achieving desired operation of system. The Peakingswitch pressure will be kept at maximum for achieving maximum load voltage butduring this condition output voltage will not have flat top. The Peaking switch isoperated in 60 to 80 % of its maximum value for achieving the flat top pulse.Required voltage achieved using altering the Marx generator erected voltage.Pressure value and Ratio was obtained through series of experimentations.

[0043] Referring to figure 3, the present disclosure shows the equivalentcircuit of proposed PPS to achieve flat pulse width. Designed parameters of MG,peaking capacitor and peaking switch and operating pressure of peaking switchplays the major role for achieving flat pulse. Parameters involved during thedischarge phase of Marx generator and peaking capacitor are considered in thisequivalent circuit. Parameters involved in the charging phase are ignored as thoseparameters do not affect the output pulse parameters. Output switch (So) will beclosed after the erection of Marx generator, which happens after the Marx stagecapacitor reaches required voltage. Now the Marx generator charges the Peakingcapacitor through Marx Series inductance (Lmarx) and Inductance of Peakingcapacitor (Lp). After 60 to 80 % of Maximum value of peaking switch breakdownvoltage, the peaking switch breaks down. Now, Peaking capacitor discharges to loadthrough Lp and Lpk ( Both value is very low compared to Lmarx). All the aboveparameters are designed such that the flat pulse width of ~ 70 ns can be achievedacross fixed load impedance.

[0044] Referring to figure 4, the proposed circuit was simulated usingOrcad and fig 4 shows the flat pulse of 70ns obtained in simulation.

[0045] Referring to figure 5, the proposed system was built and alsoexperimentally tested with fixed load impedance and flat pulse of ~ 70ns wasachieved as shown fig 5.

[0046] The foregoing description of the invention has been set merely toillustrate the invention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the substance of the invention may occur toperson skilled in the art, the invention should be construed to include everythingwithin the scope of the invention.[List of References]200- A System for high voltage and high current flat-topped pulse generation201-Marx Generator (Cmarx)202-Output Switch (So)203-Peaking Capacitor (Ppc)204-Peaking Switch (Spk)205-Load

Claims

1. A system for high voltage and high current flat-topped pulse generation (200), the system comprising: a Marx Generator configured to generate the high voltage and the high current; an output switch (So) connected to the Marx Generator, the output switch configured to discharge the high voltage generated by the Marx generator; a peaking capacitor (Cpc) connected to the output switch (So), the peaking capacitor configured to be charged by the generated high voltage through the output switch; and a peaking switch (Spk) connected to the peaking capacitor, the peaking switch configured to discharge the peaking capacitor through a load to generate the flat top pulse at the load. .

2. The system (200) as claimed in claim 1, wherein the Marx Generator comprising: a plurality of stage capacitors (Cn) to generate erected capacitance (Cmarx), wherein the plurality of stage capacitors (Cn) are interconnected with a plurality of spark-gap switches in a way such that the plurality of stage capacitors are in parallel with a charging power supply, wherein after the charging voltages of plurality of stage capacitors (Cn) reach the breakdown voltage of the corresponding plurality of spark-gap switches, all the stage capacitors (Cn) are connected in series during discharge and generating the erected capacitance (Cmarx), and wherein the breakdown voltage is decided by a gap spacing and a gas pressure in the spark-gap switch; and a plurality of charging and ground inductors (Ln) to charge the stage capacitors (Cn), wherein the plurality of charging and ground inductors (Ln) are connected in series with the plurality of stage capacitors (Cn), and during the discharge of the stage capacitors (Cn), erected series inductance (Lmarx) is based on stage capacitance, spark gap and connecting leads in the discharge path of Marx Generator.

3. The system (200) as claimed in claims 1 to 2, wherein the Marx Generator can operate from 100- 150Hz repetition rate at voltage and current of 400kV-600kV and 10 kA-15kA.

4. The system (200) as claimed in claims 1 to 3, wherein the output switch (So) is in open condition during charging phase of the stage capacitors (Cn).

5. The system (200) as claimed in claims 1 to 4, wherein duration of the flat top pulse is based on Cmarx to Cpc value along with Peaking switch pressure.

6. The system (200) as claimed in claims 1 to 5, wherein the Cmarx to the Cpc ratio is at least 1.5 times for achieving the flat top pulse.

7. The system (200) as claimed in claims 1 to 6, wherein the peaking switch (Spk) is operated in 60% to 80% of its maximum value for achieving the flat top pulse.

8. The system (200) as claimed in claims 1 to 7, wherein flat pulse width of 70 ns duration can be achieved across the load.

9. The system (200) as claimed in claims 1 to 8, wherein the plurality of sparkgap switches is triggered by a plurality of linking resistors (Rt).

10. The system (200) as claimed in claims 1 to 9, the flat-topped pulse is generated by varying the pressure p1 of the peaking spark-gap switch (Spk).

11. A method for high voltage and high current flat-topped pulse generation, the method comprising the steps of: generating the high voltage and the high current by configuring a Marx Generator; discharging the generated high voltage by configuring an output switch (So) connected to the Marx Generator; charging a peaking capacitor (Cpc) connected to the output switch (So) by the generated high voltage through the output switch; and discharging the peaking capacitor through a load by configuring a peaking switch (Spk) connected to the peaking capacitor.

12. The method as claims in claim 11, wherein the method includes: charging a plurality of stage capacitors (Cn) to generate erected capacitance (Cmarx), wherein the plurality of stage capacitors (Cn) are interconnected with a plurality of spark-gap switches in a way such that the plurality of stage capacitors are in parallel with a charging power supply, wherein after the charging voltages of plurality of stage capacitors (Cn) reach the breakdown voltage of the corresponding plurality of spark-gap switches, all the stage capacitors (Cn) are connected in series during discharge and generating the erected capacitance (Cmarx), and wherein the breakdown voltage is decided by the gap spacing and a gas pressure in the sparkgap switch; and charging the stage capacitors (Cn) by a plurality of charging and ground inductors (Ln) connected in series with the plurality of stage capacitors (Cn), and during discharge of the stage capacitors (Cn), erected series inductance (Lmarx) is based on inductance of stage capacitance, spark gap and connecting leads in the discharge path of Marx Generator.

13. The method as claimed in claims 11 to 12, generating 100- 150Hz repetition rate at voltage and current of 400kV-600kV and 10 kA-15kA by the Marx Generator.

14. The method as claimed in claims 11 to 13, wherein configuring / serving the output switch (So) in open condition during charging phase of the stage capacitors (Cn).

15. The method as claimed in claims 11 to 14, wherein deciding duration of the flat top pulse by the Cmarx to Cpc value along with Peaking switch pressure.

16. The method as claimed in claims 11 to 15, wherein the Cmarx to the Cpc ratio is atleast 1.5 times for achieving the flat top pulse.

17. The method as claimed in claims 11 to 16, wherein operating the peaking switch (Spk) in 60% to 80% of its maximum value for achieving the flat top pulse.

18. The method as claimed in claims 11 to 17, wherein achieving flat pulse width of 70 ns duration.

19. The method as claimed in claims 11 to 18, wherein triggering the plurality of spark-gap switches by a plurality of linking resistors (Rt).

20. The method as claimed in claims 11 to 19, wherein generating the flat-topped pulse by varying the pressure p1 of the peaking spark-gap switch (Spk).