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Dr David Cook Power Electronics, Machines and Control Group

High Voltage, High Power, High Frequency Converters for Industrial Applications. Dr David Cook Power Electronics, Machines and Control Group. Applications of HV PSU. High voltage power supplies are used in range of medical, scientific, industrial and defence applications

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Dr David Cook Power Electronics, Machines and Control Group

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  1. High Voltage, High Power, High Frequency Converters for Industrial Applications Dr David Cook Power Electronics, Machines and Control Group

  2. Applications of HV PSU • High voltage power supplies are used in range of medical, scientific, industrial and defence applications • Treatment of tumours • Particles physics research, e.g.: CERN, LANL, ORNL, • Emerging power station technology, e.g.: ITER • Industrial processing of rock and mineral • Radar and EW

  3. Conventional Power Supply High Voltage Rectifier Filter Grid Voltage, Line Frequency Transformer Crowbar Load AC LF input x3 Shunt Thyristor Rectifier High Voltage, Line Frequency Transformer

  4. Why HV, HF? • Techniques used at the University of Nottingham utilise high frequency (20kHz) resonant circuits. • High frequency operation significantly reduces the size of the high voltage transformer and input/output filters • Estimated that 20kHz transformers may are approximately 1% the size of line frequency counterparts • Resonant circuits allow for soft-switching (ZVS/ZCS), therefore allowing high power at high frequency • Allows for highly compact power converter in many applications where space and weight are critical

  5. Current and RecentResearch Projects

  6. Long PulseExisting Technology • Disadvantages • Very large capacitor bank (energy storage ~80kJ) • Crowbars Required • Large filter components required to limit “flicker”

  7. Long PulseExisting Technology • Large Utility frequency transformer and rectifier • Poor input quality • Huge DC capacitor bank (need low droop during pulse) • 2 Crowbars • High voltage series switch

  8. Long Pulse New Technology – direct modulation (Mike Bland)

  9. Long Pulse Converter Voltage gain / frequency characteristics of resonant tank Simulation result

  10. Long Pulse Converter Some key features • Long Pulse or CW operation • High power factor input (low harmonic content) • Intelligent recharging of Cdc between shots eliminates flicker • Soft switching – high power, high frequency operation • HF transformer for reduced size • HF + multiphase operation gives high ripple frequency • Small output filter • low energy storage – small energy dump during fault • Direct modulation of HF inverter for long pulse operation

  11. Long Pulse Modulator: Assembly Wave guide Solenoid Cathode Voltage Monitor Magnetron Input from Pulsed PSU Control Unit Auxiliary PSUs Pulsed PSU (UoN) Heater Supply Industrial experimental prototype

  12. Long Pulse Modulator: Results Experimental result obtained from operation with Magnetron load

  13. CW Converter Direct Conversion Approach CONTROL 3-phase to 1-phase matrix Resonant tank and transformer Rectifier + filter Filter LOAD AC Supply

  14. CW Converter Resonant tank Input “matrix” Predictive control of resonant tank every ½ cycle of resonance Line Filter S1 S3 S5 AC LF input Output Filter/Rectifier S2 S4 S6 HF transformer Switches S1-S6 commutated when tank current passes through zero – soft switching Bi-directional switch

  15. CW Converter Some Key Features • “No” energy storage • Potential for small size • CW only • Soft switching of matrix • High efficiency • High power factor input (low harmonic content) • High operating frequency • Small input filter • HF transformer for reduced size • Small output filter • low energy storage – small energy dump during fault

  16. CW ConverterResults DC Output Waveform • Experimental result • Converter producing 25kV DC • 25kW Output • Simulation result • Converter producing 25kV DC • 25kW Output

  17. CW ConverterResults Phase Current • Experimental result • Converter producing 25kV DC • 25kW Output • Simulation result • Converter producing 25kV DC • 25kW Output

  18. High Efficiency Pulsed Power Supplies (Fabio Carastro) • Scalability and reliability of pulsed power supplies utilising IGBT’s • Thermal cycling of IGBT during pulsed operation • Asses reliability implications • 250kW (500J) test rig to asses thermal cycling • Consider different topologies for high power (500kW+) units • 500kW prototype in construction at partner company

  19. Electrostatic Precipitator(Vivek Tailor) • Knowledge Partnership with Castlet Ltd. • World leader in manufacture of Electro-Static Precipitators • Used to remove particulate emissions from power station exhaust. • Existing supplies are based on line-frequency approaches • Competitors are starting to introduce supplies utilising high frequency techniques to the market • More responsive • “Pulsed Operation” • Can be mounted on the chimney (space saving)

  20. Electrostatic Precipitator(Vivek Tailor) • 100kV, 2Amp Unit • LCC Resonant circuit • Phase Control • Highly demanding load (short and open circuits) • Less stringent power quality and output ripple specifications H-Bridge High Voltage, High Frequency Transformer Cockcroft-Walton Multiplier Resonant Tank (LCC)

  21. Ultra Compact Capacitor Charging System • Design of a 40kJ/s capacitor charging system for high voltage (20kV) applications • Ultimate requirement is for minimised converter volume / height (100mm) • Weight and efficiency are a secondary consideration • “Twin Shot” Application: Only required to charge the output capacitor twice. • Then de-activated until converter has cooled sufficiently

  22. High Power, High Voltage, High Frequency Transformers for Switching Converters (Todor Filchev) • Follows on from previous PPARC project, “Power Supplies for High Power RF Systems” . • Optimal design of the transformer/rectifier was identified as a critical component in order to fulfil the potential of new converter concepts. • In particular a reduction in size, weight and cost whilst maintaining reliability. • Required to generate the knowledge and confidence such that industrial exploitation of compact (HF) power converters can become a reality

  23. Background to Project • Key requirement of emerging high frequency high voltage converters is the requirement for step up transformers • Present knowledge is based on (at best) experience at line frequency • Many factors influencing transformer design are frequency dependant

  24. HVHF Transformer Main concern is the HVHF Transformer • High voltage insulation requirements (Choice of materials is essential) • Leakage inductance/stray winding capacitance(LC tank interaction) • Core loss and heat dissipation (reduced efficiency) • Rectification and output terminal connections Equivalent transformer model.

  25. Thank you Any questions?

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