Solid State Pulse Modulators - Basic Concepts and Examples - Jürgen Biela S. Blume, M. Jaritz, G. Tsolaridis

Solid State Pulse Modulators - Basic Concepts and Examples - Jürgen Biela S. Blume, M. Jaritz, G. Tsolaridis 1

Energy related Research @ D-ITET / ETH Zurich Professorship in HIGH POWER ELECTRONICS Start Date: 1. August 2010 Medium Voltage Laboratories 1 Permanent Lab-Engineer è 12 Ph.D. Students @ 2017 Research in close Collaboration with Industry 60-70% External Funding

Research Topics @ Laboratory for High Power Electronic Systems (HPE) Major Research Topics Comprehensive Modelling of Converter Systems è Multi-Criteria Optimisation è Efficient Design of Converters è Identify Technological Barriers New Topologies / Modulation Advanced Passives Control Methods Modulation Cooling Topologies Semiconductor Passives Design

New High Power Laboratory - Facilities 3 Reconfigurable Faraday Test Cells 3 Reconfigurable Fence-Test Cells Max. Cell Size: 57m 2 Sources: Ø 0..400V/800V 250kVA Ø 0..25kV AC 250kVA Ø 0..35kV DC 250kW Ø 0..2kV DC 100kW /1.2kA (Bidirectional) 150kW Water Cooling 2 x 30kW Air Cooling 2t Crane

Solid State Pulse Modulators

Pulsed Power Definition of Output Voltage Pulse Shape Typical pulse shapes / requirements - Time to flat top (Fast rise and fall times) - Low overshoot - Flat pulse top / low droop - Low reverse voltage - Voltage-time area (klystron)

Reproduceability - Max. deviation between consecutive pulses - Different definitions/requirements exist: (Example: 3 measurement points) Max! V k,p1 V k,pj k=1...3 ( ) j=2...100 10ppm 3σ

Pulsed Power / Pulse Length for typical Applications 1) Basic concepts based on - Direct switch - Marx-type - Pulse transformer - DC-DC converter 2) 3µs SwissFEL modulator 3) 140µs CLIC modulator - Precise charging - Active bouncer - System design 4) 3.5ms ESS modulator - System concept - Transformer design 5) Pulsed current source - System concept

Basic Concepts for Solid State Pulse Modulators

Typical Topology 0f a Solid State Pulse Generator System Typical topology of a solid state pulse modulator - AC/DC rectifier unit - DC/DC converter for charging C-bank / voltage adaption - Pulse generation unit - Load e.g. klystron

Typical Topology 0f a Solid State Pulse Generator System Typical topology of a solid state pulse modulator - Isolation with 50Hz transformer or - Isolated DC-DC converter

Solid State Switches

Solid State Switches Pulsed Power Pulsed power è <GW Pulse length è typ. >µs-range Si IGBT 4.5kV 4kA (pulsed) SiC MOSFET 1.2kV ~1kA (pulsed) (~800kW)

Solid State Switches Dynamic Performance Higher breakdown voltage è Slower switching transients (esp. turn-off delay) è Available minimal module current is relative high E.g. 800A @ 4.5kV / 250A @ 6.5kV Si IGBT 4.5kV 4kA (pulsed) SiC MOSFET 1.2kV ~1kA (pulsed) (~800kW) Transient performance IGBT SiC MOSFET Turn-on delay time 700ns 75ns Rise time 550ns 70ns Turn-off delay time 3.5µs 170ns Fall time 700ns 45ns

Solid State Switches Pulse Lengths / Pulsed Power

Modulator with High Voltage Switch Simple concept, but high no of switches High voltage supply required Voltage balancing of switches required è Reduction of switch operating voltage è Additional losses (balancing circuit + high no of switches) è Parasitic oscillations possible Isolated gate-drives/supplies required Limitation of short circuit current is critical (L required) Pulse switches need to be synchronized Variable pulse length possible

Modular: Marx-Type Voltage pulse by adding capacitor voltages Variable pulse voltage and arbitrary length possible Synchronous triggering of switches NOT required è Improved robustness Isolated gate-drives / gate-supplies

Modular: Marx-Type Pulse Generation Voltage pulse by adding capacitor voltages Variable pulse voltage and arbitrary length possible Synchronous triggering of switches NOT required è Improved robustness Isolated gate-drives / gate-supplies Problem: Energy in case of short circuit (L required / bipolar Marx)

Modular: Marx-Type Charging I Voltage pulse by adding capacitor voltages Variable pulse voltage of arbitrary length possible Synchronous triggering of switches NOT required è Improved robustness Isolated gate-drives / gate-supplies Problem: Energy in case of short circuit (L required / bipolar Marx) Capacitor charging via resistor/inductor LC (+ Parasitics) è Oscillations possible (è high reproduceability?)

Modular: Marx-Type Charging II Voltage pulse by adding capacitor voltages Variable pulse voltage of arbitrary length possible Synchronous triggering of switches NOT required è Improved robustness Isolated gate-drives / gate-supplies Problem: Energy in case of short circuit (L required / bipolar Marx) Capacitor charging via resistor/inductor or switch/diode (è Long pulses) LC (+ Parasitics) è Oscillations possible

Modular: Marx-Type + PWM Cell Voltage pulse by adding capacitor voltages Variable pulse voltage of arbitrary length possible Synchronous triggering of switches NOT required è Improved robustness è Droop compensation / pulse shaping (PWM) Isolated gate-drives / gate-supplies Problem: Energy in case of short circuit (L required / bipolar Marx) Capacitor charging via resistor/inductor or switch/diode (è Long pulses) LC (+ Parasitics) è Oscillations possible

Modular: Marx-Type / Direct Switch - Arc Energy Assumptions: - i L =0 at t=0 i L = V p - Switch turns off at Z t doff W T 1 = L s Z tdoff 0 V Arc - Energy in L s is dissipated in arc/diode t V Arc i L dt = è Large L s required to limit energy W ges = W T1 +W T2 ( larger L s for i L (t=0) 0 ) Equivalent Network

Pulse Transformer Based High pulse voltage is generated by transformer Adaption to switch operating voltage possible Series and/or parallel operation of switches Series: Voltage balancing Parallel: Current balancing è Amount of switches reduced è Better reliability è Less separate gate drives As a first approximation: Primary voltage does NOT influence pulse shape (trafo parasitics) Pulse length is limited by transformer

Pulse Transformer Based Matrix Transformer Separate windings/transformers per switch è Voltage/current balancing is inherently achieved Name: Split Core / Matrix Transformer / Inductive Adder (same basic concept) (Relative old basic concept)

Pulse Transformer Based Current Balancing in Matrix Transformer Separate primary windings on 2 cores: - Inherent current balancing - 2 windings + 2 cores è Series connection on secondary side (flux adder) I pri,1 I pri,1 = N 2 N 1 I sek V DC,1 S M,1 D f,1 I sek 2D V DC,2 S M,2 D f,2 I pri,2 N 1 :N 2 N 1 :N 2 V sek R Load I pri,2 = N 2 N 1 I sek

Pulse Transformer Based Reduced L s in Matrix Transformer I Separate primary windings on 2 cores: - Inherent current balancing - 2 windings + 2 cores è Series connection on secondary side (flux adder) - Secondary turns è N S /2 N p : N S /2 N S /2 N p : N S N p : N S /2

Pulse Transformer Based Reduced L s in Matrix Transformer II Separate primary windings on 2 cores: - Inherent current balancing - 2 windings + 2 cores è "Virtual series connection" - Secondary turns è N S /2 Advantages: - N S /2 è Leakage inductance ê - No series/parallel connected IGBTs Disadvantages: - Doubling of core volume! L σ,matrix ~ 2Vol # " N 2 $ & % 2 ~ L σ,single 2 T "#$% ~ L ) C + Damping~ L ) C + N p : N S /2 N S /2 N p : N S N p : N S /2

Pulse Transformer Based Cone Shape Wdg. in Matrix Transformer Winding shape: - Parallel windings è Large volume between Pri/Sec è Large leakage inductance - Cone shape è Large distance @ high voltage è Volume / 2 -> Leakage / 2 - Offset voltage possible è Cathode heating @ high potential V V S M,1 D f,1 I pri,1 V sek R Load V DC,1 S M,2 D f,2 I pri,2 V DC,2

Pulse Transformer Based 2 IGBTs on 1 Core Pulsed power per switch: 10-11MW è 2 separate switches per core - "Per core" 20-22MW - Current sharing between 2 switches per core è Synchronization è Separate DC capacitors è Separate Leakage inductance V DC,1 V DC,2 S M,1 D f,1 S M,2 D f,2 I pri,1 I pri,2 V sek R Load Doubling the pulsed power V sek R Load I pri,1 I pri,3 S M,1 D f,1 S M,3 V DC,1 D f,3 V DC,3 I pri,2 I pri,4 S M,2 D f,2 S M,4 V DC,2 D f,4 V DC,4

Example: 127MW Pulse Transformer for SwissFEL Core material: - SiFe 50µm / (2605SA1) Primary windings: - 3 kv input voltage - Copper foil, d = 1mm Secondary windings: - 370 kv output voltage - 21 Turns è 17.6 kv per turn - Round conductor, d = 3mm Dimensions (Secondary): - Length: 1190mm - Width: 525mm

DC-DC Converter Based PSM Modulator Adding output voltage of isolated switched DC-sources è Generate primary voltage for transformer Pulse length limited by pulse transformer Small C-bank possible with droop compensation / PWM-module Pulse shaping possible (steps + PWM for long pulses) 50Hz transformer for isolation of DC-sources

DC-DC Converter Based Adding output voltage of isolated DC-DC converters - Parallel in / serial connected out è Compact transformer (HF switching) Pulse rise time relative slow è Suitable for long pulses (typ. > 1ms) Small C-bank possible (Droop compensation) Pulse shaping possible DC-DC converters e.g.: - Resonant converter - Single active bridge

Topology Comparison Direct Modulator Marx Type Matrix Pulse Trafo DC-DC Converter Transformer Based Arbitrary Pulse Length Arbitrary Length Fast Rise Time Inherent Short Circuit Current Limitation Adaption to Switch Operation Voltage Power Electronics on Low Voltage High number of Switches No Sync of Semiconductors or Modules necessary High # of Switches

Solid State Pulse Modulators Technologies & Examples 1) Basic concepts based on - Direct switch - Marx-type - Pulse transformer - DC-DC converter 2) 3µs SwissFEL modulator 3) 140µs CLIC modulator - Precise charging - Active bouncer - System design 4) 3.5ms ESS modulator - System concept - Transformer design 5) Pulsed Current Source - System concept

Solid State Pulse Modulators Prototypes Designed @ HPE

Short Pulse Modulator (~ µs-range) 127MW/370kV/3µs Solid State Modulator with Ultra High Precision for SwissFEL è Talk by Mr. Frei

Medium Long Pulse Modulator (~ 100µs) Ultra High Precision Klystron Modulators for Compact Linear Colliders (CLIC)

CLIC System Specifications Pulse voltage 150kV - 180kV Pulse power 29MW Pulse duration 140µs Repetition rate 50Hz Rise/fall time 3µs + 5µs settling Max. pulse droop 0.85% Reproducibility 100ppm System efficiency > 90% (AC to output pulse)

Modulator System - Overview

Modulator System - Overview Pulse voltage 150kV - 180kV Pulse power 29MW Pulse duration 140µs Repetition rate 50Hz Rise/fall time 3µs + 5µs settling Max. pulse droop 0.85% Reproducibility 100ppm System efficiency > 90% (AC to output pulse)

AC/DC System PFC rectifier Input voltage V IN = 400V AC Output voltage V Out = 650-800V DC Output power P Out = 240kW Controlled via PLC

Ultra-Precise Charging Converter Triangular current mode (TCM) 6 interleaved converters Input voltage V IN = 750V Output voltage V Out = 3kV ± 23mV Output power P Out = 6 x 40kW Switching freq. f S = 70 200kHz Reproducibility ± 8ppm Range of ZVS operation is limited R Sn,D1a R Sn,D1n L 1 C Sn,D1a C Sn,D1n D 1a D 1n S 1a C Sn,S1a R Sn,S1a D 1 V in C in S 1 C out v out + - S 1n C Sn,S1n R Sn,S1n

Ultra-Precise Charging Converter Switching cycles are independent of each other Cycle-to-cycle feedback control Required I max or t on calculated for the next cycle I max =0..160A è ΔV load =0..80mV

Control Hardware Factors influencing Repeatability Input voltage measurement SNR Output voltage measurement SNR Switch current measurement SNR ADC resolution Quantization related errors DAC resolution Converter limitations (e.g. max. I L ) Finite resolution in digital domain Switching signal jitter

Ultra-Precise Charging Converter Triangular current mode (TCM) 6 interleaved converters Input voltage V IN = 750V Output voltage V Out = 3kV ± 23mV Output power P Out = 6 x 40kW Switching freq. f S = 70 200kHz Reproducibility ± 8ppm / 1s System reproducibility ± 23mV charger ± 27mV bouncer incl. transformer ± 50mV / 1s è 100ppm / 6s (99.7%)

240kW Booster Rack ( 6 x interleaved) 6 x 40kW booster in rack 6-fold interleaving Master set-point/freq. is constant Slave set-point è Phase shift 50Hz repetition rate Range of ZVS operation is limited

Modulator System - Overview Pulse voltage 150kV - 180kV Pulse power 29MW Pulse duration 139µs Repetition rate 50Hz Rise/fall time 3µs + 5µs settling Max. pulse droop 0.85% Reproducibility 100ppm System efficiency > 90% (AC to output pulse)

Active Bouncer Topology Interleaved buck-boost converter with short circuit switch Voltage levels: - V main = 3kV - V B,in = 450V - V B,out = 0 300V è 10% droop in main capacitor Aim: 100ppm system repeatability è 24-fold interleaving ( 4 units à 6 bouncer ) è Effective ripple frequency up to 2.4 MHz è < 5 ppm ripple induced by bouncer è Parallel redundancy possible

Active Bouncer + Capacitor Bank 4 identical units 6 bouncer circuits per unit 1 discharge circuit per unit 3-layer bus bar 2 storage capacitors Modular system concept Slide-in connections Discharge circuit Bouncer modules Short circuit switch Buck-boost switches Control board Main capacitor bank

Switching Unit Press-Pack IGBTs 4 identical units Pulse switch: StakPak pulse IGBT Premagnetisation: Standard IGBT High turn-off current handling IGBT gate drive with - Overcurrent protection - Overvoltage protection - di/dt detection - Pulse current detection - Temperature monitoring - Turn-on time monitoring - UVLO (aux. supply & capacitor-bank)

Pulse Transformer Matrix transformer in oil Pulse voltage 180kV SiFe core (50µm tape) 2 cores / 4 IGBTs (switching units) Turns ratio (4 : 62) x 2 è 4:124 Weight ~ 1.6t Built by Pikatron H x B x T: 120cm x 76cm x 66cm

Pulse Transformer Transformer Model Validation Matrix transformer in oil Pulse voltage 180kV SiFe core (50µm tape) 2 cores / 4 IGBTs (switching units) Turns ratio (4 : 62) x 2 è 4:124 Weight ~ 1.6t Built by Pikatron

Modulator System - Design Energy in klystron in case of arc: < 10J (without cable) System efficiency 90% Peak power 29MW (35MW) Pulse voltage 150kV - 180kV 4 pulse units Designed & Built by HPE

Pulse Measurement Without Active Bouncer Measurement @ Nominal pulse voltage Nominal pulse current Without droop compensation Single pulse full voltage 10 pulse burst @ 20 Hz

Pulse Measurement With Active Bouncer Measurement @ 1/3 pulse voltage 1/3 pulse current

Long Pulse Modulator (> 1ms) Resonant DC-DC Converters for Long Pulse Klystron Modulators

European Spallation Source (ESS) Pulse power 2.88MW Efficiency ɳ 90% Pulse voltage V Out = 115kV Pulse width T PW = 3.5ms Rise/fall time T R, T F 150 μs

Solid State Long Pulse Modulator Pulse power 2.88MW Average power 144kW Efficiency ɳ 90% Pulse width T PW = 3.5ms Pulse voltage V out = 115kV Repetition rate P RR = 14Hz Rise/fall time T R / T F 150µs Arc energy E Arc 10J Redundancy 8 + 1

Solid State Long Pulse Modulator Resonant Converter Switching frequency > Resonance frequency è Soft switching for all MOSFETs (ZVS) è High efficiency Inherent limitation of short circuit current Switching frequency ~100kHz Module input voltage 400V Module output voltage 14.4kV Module pulse power 180kW

Transformer Design Transformer Prototype Winding N P = 2 / N S = 40 Litz wire (N p ) 18 x 405 x 0.071 Litz wire (N S ) 1125 x 0.071 Losses 130 W Volume 13.2 litre Isolation volt. 115kV Material ɛ r V BT [kv] MIDEL7131 3.2 75 Material ɛ r E max [kv/mm] POM 3.5 50 PA2200 3.8 92 PC 3 30 EPR S1 5 10

Transformer Design: E max Evaluation Field design based on charge simulation method Field shaping ring è E max < 11.5kV/m Midel7131 isolation oil Litz wire (N S ): 1125 x 0.071mm

Transformer Design - Field Conform Design Comparison of oil field design curves with critical averaged field paths E avg Only tangential equipotential lines on insulation surfaces E 567 (z) = 1 @ z = E z> dz > A

Partial Discharge Measurement of Pulse Transformer Omicron MPD600 PD measurement system Pulse transformer tested @ 90kV RMS Long term test (60 min) Short term test ( 5min)

Simulation Results: Full System 2 x 8 Modules System Parameters V out = 115kV P out = 2.88MW I out = 25A f = 100-110kHz

Full System Setup built by Ampegon

Solid State Bipolar Pulsed Voltage/Current Source for Bumper/Septum Magnets & Plasma Research

HIL for DC Circuit Breaker Emulation of fault currents in DC grids è Pulsed arbitrary current source 30 ka output current at up to 10 kv 200 A/μs max. current gradient up to 20 ms pulse length

Pulsed Current Source V1.0 Basic Operation System topology: Modular Multi-Level Marx Type Converter (M 3 TC) Interleaved ZVS freq. variable 3-level-converter 30 ka output current at up to 10 kv 200 A/μs max. current gradient up to 20 ms pulse length

Pulsed Current Source - 1 st Prototype Output Voltage V out,max 5.5 kv Output Current I out,max 1.4 ka Current Gradient di / dt 2 A /µs Operation Period t Pulse 20 ms

Extension: Bipolar Pulse + DC Current + Higher Dynamic Max. output voltage Max. pulse current Current gradient 10 kv 30 ka ±200 A/µs Pulse length @ I max 10 ms Current ripple @ I max <1 % Arbitrary waveform Continuous current High modularity Bipolar output voltage DC operation Typical loads ü 20 ka ü ü ü Resistive, inductive, fluctuating (arcs)

Example for highly dynamically changing loads (arc) Load voltage change: Arc voltage stochastically changing > 500V in 2µs Behavioral arc model based on measurements New controller concept Load current: +/- 10% High di/dt 20 ms operation time

New hybrid control concept Hybrid controller: Hysteresis control Time optimal transient response Good disturbance rejection PI average current control Zero static error Constant switching frequency Phase-shifting control Minimum ripple @ steady state

Conclusion Modulators with matrix transformer - Charging circuit - Active bouncer - Transformer design - Pulse unit - Gate drive Robust & simple concept Pulse lengths: 3µs < T P < 300µs Tested 3µs system - Swiss-FEL Tested 140µs system - CLIC Modulators with DC-DC converter - Basic concept - Prototype system Pulse lengths: 500µs < T P Tested 3.5ms system ESS DC & pulsed current source - Basic concept - Prototype system - Advanced control Direct Modulator Marx Type Matrix Pulse Trafo DC-DC Converter

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