NPSS Distinguished Lecturers Program

Transcription

1 NPSS Distinguished Lecturers Program Solid-state pulsed power on the move! Luis M. S. Redondo Lisbon Engineering Superior Institute (ISEL) Nuclear & Physics Center from Lisbon University (CFNUL) EnergyPulse Systems, Lda (EPS) Lisbon, Portugal

2 o Pulsed-Power o o o Outline what is it & some facts Industrial applications Pulse generation o o o o o o Concept - energy storage Switching - semiconductors o o Opening switch, inductive storage: SOS diodes Closing switch, capacitive storage: Thyristors, MOSFETs, IGBTs, JFETs, Topologies/techniques for pulse generation Protection, Triggering, thermal considerations How to deal with semiconductor limitations Future trends SiC o Example o Summary 11/30/2012 2

3 Pulsed Power? The science and technology of accumulating electrical energy over a relatively long period of time, followed by its released in a single short pulse or a repetitive sequence, thus increasing the instantaneous peak power, enhancing the properties of a product or a technique. High peak power Low average power Pulsed not ac or dc Enhance bio & physic-chemical effects What makes it so unique? The concept that extremely high peak powers can be delivered during precise times without the demand for highly average power sources, used in custom dc or ac power systems. 11/30/2012 3

4 Facts about Pulsed Power! The German Erwin Otto Marx invented in 1923 the cascaded generator that allows the generation of transient high voltages, known as the Marx generator. 1.2/50 Impulse voltage TU Dresden, Germany Until 70s the research in Pulsed Power was confined to National Laboratories in the US and USSR, and a few industries, but the results were generally secret. The research was restricted to military and high energy physic applications. The first biennial Pulsed Power Conference was organized in Lubbock, Texas, in 1976, and the IEEE Transactions on Plasma Science becomes the official R&D journal for Pulsed Power. With the end of the could war in 1989 the Pulsed Power community starts searching for industrial pulsed power applications. 11/30/2012 4

5 Driving forces for R&D in Pulsed Power Transfer from high energy single pulses to lower energies, repetitive pulses, efficient and reliable systems Industrial applications 11/30/2012 5

6 Industrial applications in Pulsed Power Where moderate pulse energies, repetitive pulses, efficient, portable, reliable and cost effective modulators are needed. Loads: R, liquids RC, gases, plasmas RL, inductor, transformer In average: up to khz, µs to ms, ka, 10 s kv. Biological effects: - food processing (extraction & sterilization) - plasma sterilization - medical treatment (e.g. cancer) - crop growth Streamer discharges in gases: - exhaust gas treatment - ozone generation Discharges in liquid or liquid-mixture: - water treatment - engine ignition Material processing: - implantation & deposition (surface change) - magnetic forming, welding & cutting - nano particles synthesizing - concrete recycling - laser (material ablation & surface annealing) 11/30/2012 6

7 Pulse generation 11/30/2012 7

8 Pulse generation concept Fixed or mobile source of electrical power Primary Energy Source Energy Storage Switching (Shaping) Pulse technique Load High/low conductivity, RC Inductive, L Switching sets the performance of the modulator & for Industrial Applications Shamiloglu, E., Barker, R.J., Gundersen, M., and Neuber, A.A. PROCEEDINGS OF THE IEEE, VOL. 92, NO. 7, JULY 2004 Solid-state switches: - medium peak power - high-repetition rate - compactness - long lifetime - efficiency 11/30/2012 8

9 Pulse generation storage vs switching Capacitive storage Closing switch Inductive storage Capacitive vs inductive energy density Opening switch 11/30/2012 9

10 Switching Technology 11/30/

11 Solid-state switches for industrial applications SCR, silicon-controlled rectifier GTO, gate turn-off thyristor IGCT, integrated gate-commutated thyristor MOSFET, metal-oxide semiconductor field-effect transistor IGBT, insulated gate bipolar transistor, IEGT, injection-enhanced gate transistor Families: JFET, Junction Field Effect Transistor - HV PIN diode and SOS diodes - Thyristors and turn off Thyristors devices: SCR, GTO/GCT, IGCT, MCT - Metal Oxide Semiconductor technology: MOSFET, IGBT, IEGT - Power JFETs and derived devices, normally on: SIT, SITh (SiC technology) 11/30/

12 Opening switch - SOS Diodes Semiconductor Opening Switches (SOS) are modified high-voltage diodes, PIN, using a P + PN - N + structure with gradual doped P layer. They are optimized to exhibit relatively slow reverse recovery ( ns) but abrupt recovery (very fast reverse decay) 5ns. Inductive energy storage Switch ka in ns opening times, with uniform distribution of reverse voltage (kv) in series stacked devices, with average power of 10 s kw. 11/30/

13 Closing switch on & off Thyristors Turn-on SCR Turn-off GTO Turn-off IGCT Incorporate distributed gate drive Basic Trigger circuit Modern optically activated LTT, Light triggered Thyristor or LASCR, Light Activated SCR 11/30/

14 Closing switch MOSFET vs IGBT IGBT (hybrid device) PT-IGBT, extra P + layer in collector NPT-IGBT, substituting N + by a P + layer P + injects holes in N - layer reducing voltage droop by conductivity modulation. MOSFET (unipolar device) Fast t rise & t fall Limited hold-off voltage (1 kv) due to on-resistance Similar trigger circuits, low power for charge/discharge input capacitance 11/30/

15 Closing switches SIT & SITh Normally-on switches, can be turned-off by a negative voltage on the gate electrode. SIT SITh 5.5kv/600A Candidate for replacing multiple MOSFETs. R on similar to MOSFET!!!! Used for pulse generation as an opening switch in inductive circuits, like SOS diode. The SITh behaves as a controlled diode. High power capability (better than MOSFET) and relatively fast switching performance (better than IGBT). Cascode 11/30/

16 Semiconductor stacks - Series To overcome the power semiconductor s limited hold-off voltage: Guarantee synchronization & voltage sharing: - Static, R - Dynamic, RC Independently trigger Higher complexity Cascode topologies Commercial Series switch 11/30/

17 Semiconductor stacks - Parallel To overcome the power semiconductor s limited current ratings: Guarantee current sharing and synchronization: Bipolar devices Temperature coefficient: - positive, MOSFETs, SITs - negative, diodes, SCR, GTO, IGBTs solution - matched devices - current sharing transformers or coupled inductors - current feedback control techniques - small resistors in series IGBTs MOSFETs 11/30/

18 Protection Protections: - Snubber circuis: - L in series for decreasing di/dt; - RC in parallel for lowering dv/dt; - TVS/MOV/zeners in parallel for over-voltage TVS, Zener MOV, TVS Zener, TVS IGBT series Static & dynamic voltage sharing & dv/dt protection Transistor with RCD&L SCR with RC&L 11/30/

19 Protection Protections: - Fuses!!! -v ce monitoring for over-current protection Hard switch-off Drive circuits with integrated protections IR Soft switch-off (limits over-voltage) Concept 11/30/

20 Technology future trends Si solid-state is not dead... long live SiC solid-state. SiC is one of the wide band-gap semiconductor materials (AsGa, C, GaN) Switching: Compactness, high-speed, high-efficiency, But: SiC still low power as compared with Si devices 11/30/

21 Thermal management Switching losses Heat sink More power More heat Static thermal model Needs dissipation Natural convection Forced air Liquid cooled + Heat sink thermal resistance R θ (ºC/W) The lower R θ the better 11/30/

22 Pulse generation techniques 11/30/

23 Pulse generation inductive storage For opening devices, ns pulse generation: Voltage peak depends on load impedance, better for capacitive loads Basic circuit For 10 s kv and ka, dozens of series and parallel devices Enhanced circuit t p = L/R Kotov, et al., IEEE Pulsed Power Conf., pp IEEE Transactions Plasma Sci., Vol. 28, no. 1, Feb /30/

24 Pulse generation direct capacitive discharge Square pulses independent of load if store energy >> pulse energy ( 10x): v V v 0 R L C dc t Ex: V dc =20kV, 50 µs/1600hz pulses into R L =1kΩ. What is C dc for v= 5%? 11/30/

25 Pulse generation associations Use of series switches to increase the hold-off voltage level. Adder circuit Direct series stack v 0 =V dc Marx generators Marx topologies for positive and/or negative pulses for any load conditions v 0 =nv dc 11/30/

26 Pulse generation using transformers for further increase the voltage output. Transformer stacking Limitations: - Average voltage zero condition imposes reset circuit; - Parasitic elements ( distributed capacitance and leakage inductance) deforms pulse shape; - Load impedance must be matched; - Low flexibility for changing pulse width and frequency. ringing! 11/30/

27 Pulse generation Pulse Forming Line Use of transmission lines for short pulse widths lower than 100 ns Single line (pulse voltage V dc /2) 50 Ω matched load 50 Ω cables 5m 50ns Pulse Forming Networks, PFNs Line impedance Z = 0 L C Transit time Blumlein (pulse voltage V dc ) t 0 = l ε r c Pulse width 2t 0 Lumped parameters line, for pulse widths >100 ns and different load impedances 100 Ω matched load + stacked lines and line transformers (100 Ω multiples matched loads). + strip lines for compact systems and other load impedances, lower ones. 11/30/

28 Half-bridge Pulse generation - Bridge topologies Full-bridge Stack associations nv dc 11/30/

29 Triggering issues Trigger pulse generation: - FPGA, PLC, Microprocessor, Microcontroller & analog circuits (noise immunity mandatory) Pulse signal sent to devices via: - Pulse transformers (galvanic insulation and power) - RC dividers - Optic fibers (galvanic insulation, low parasitic capacitance, need auxiliary power) Inverter + ring transformers Aux. Power from main circuit ABB IGCT series switch assembly 11/30/

30 Example 11/30/

31 Solid-state pulsed power on the move! 10 kv / 150 A pulse and 3.5 kw Marx type solid-state mobile modulator (80 l) Industrial applications, Food processing 1200 V off-the-shelf IGBTs 11/30/

32 Summary o Pulsed Power is pushing R&D in several scientific areas: environment, biomedical applications, food processing, industry; o Semiconductor switches are contributing to bring pulsed power closer to people: compact, portable & efficient devices; o It is important to chose the right switch and pulse technique for the application, but more general modulators are a key issue; o New material can push forward the technology; o Pulsed Power includes many scientific fields, from electric engineering to physics, from the technology to the applications; o Still it is not easy the acceptance of the technology in the industry, more work and more people are needed; o Other technologies for switching are available for industrial applications that complement solid-state. For example magnetic switches, able to handle higher power and still high repetition rates. 11/30/