Recent Approaches to Develop High Frequency Power Converters

Transcription

1 The 1 st Symposium on SPC (S 2 PC) 17/1/214 Recent Approaches to Develop High Frequency Power Converters Location Fireworks Much snow Tokyo Nagaoka University of Technology, Japan Prof. Jun-ichi Itoh Dr. Koji Orikawa (Presenter) 1

2 Power electronics laboratory Objectives Efficiency improvement & size reduction of all kinds of power sources. Research Subjects Four directions of energy conversion AC to AC AC to DC Power Electronics Laboratory DC to AC DC to DC Save the earth - Circuit topologies and control technique - Optimization of the circuit design - Development of directional technology on applications Members Associate Professor: Jun-ichi Itoh PD: 1, Ph. D: 9, M:12, B: 5 => Total: 28 persons Power Electronics saves the Earth 2

3 Field of our research Grid connected inverter Power decoupling Three Ph. D students -PV inverter, Micro inverter -Matrix converter for wind turbines -Multi-level converter -PFC( Active buffer ) etc. Theme Motor Three Ph. D students High switching frequency converter Three Ph. D students Today s contents - Motor drive(im, PMSM) - Motor design(pm) - Parameter identification method - Flywheel energy storage system - PCB implementation techniques - Applications of SiC and GaN - DC-DC converter - Gate drive circuit - Wireless power transfer - Pulse density modulation etc. etc. 3

4 High switching frequency power conversion Key technology Fundamental technologies DC bus bar analysis in printed circuit boards (PCBs) High speed & Low power consumption gate drivers Applications High switching frequency Wireless power transfer for gate drive supplies of a medium-voltage inverter High power density PWM Inverter with wide band-gap devices Frequency multiplying circuit for MHz output frequency Today s contents Wireless charger for electric assisted bicycle using EDLCs Wireless power transfer with a Rail system Several-Hundred-kHz Single-phase to Commercial Frequency Three-phase Matrix Converter 4

5 Multiple gate drive supplies of a medium voltage inverter Conventional: Special isolated transformers are used Problems - High cost and bulky due to custom designs - Reduction of parasitic capacitances is difficult Proposed method Multiple wireless power transfer with transmission coils on PCBs for multiple gate driver supplies Only PCBs are used without solid magnetic cores S 1 S 2 S 3 S 4 v inv f sw = 2 MHz f = 2MHz Transmission board #1 C 1 v in1 C D 1-4 Cost reduction & Downsizing of the isolation system Primary Secondary Insulation air-gap:5 mm #2 #3 #6 v out1 Receiver boards (6ch) MV Inv. GDU GDU 5

6 System configuration of wireless multiple power transfer 5mm Substrate spacing:5 mm Clearance and creepage distance are secured 5mm Transmission board # High frequency INV (2MHz) Series resonance capacitor C Transmission coil S 1 S 2 Receiver boards #1~#6 5mm 48V S 3 S 4 4 Controller C v inv f sw = 2 MHz 3mm 15mm Diode bridge rectifier Series resonance capacitor C 1 Receiver coil C 1 v in1 6 mm 6

7 Experimental results (Operation with gate drivers) GDU 1 #1 v out1 +15V Transmitting board C 1 DC # DC G 1 S 1 S 2 C 1 =7 pf D V PWM1 C S 3 S 4 #2 GDU 2 G 1 33nF Gate drivers are connected Capacitors are connected assuming IGBTs 48V G f sw = 2.18 MHz C =13 pf #3 #6 Inverter output voltage (Transmitting board) v inv 5 [V/div] Input voltage (Receiving board #1) v in1 25 [V/div] Output voltage (Receiving board #1) v out1 1 [V/div] Gate-emitter voltage (Receiving board #1) v GE1 2 [V/div] GDU 3 GDU 6 1kHz, ±15V Operation waveforms Enlarged view 5 [us/div] 2[nsec/div] A switching operation on all of receiver boards is confirmed v GE1 5 [V/div] 2 [ns/div] 7

8 GaN-FET Inverter & EMC filter Grid GaN-FET GaN-FET EMC filter PWM PWM Rectifier Inverter GaN-FET Inverter Motor drive system using GaN-FET M Motor Advantage of GaN-FET Fast switching L C L D GaN-FET inverter Use a PWM rectifier Sinusoidal input current C X C Y Single stage EMC filter Downsizing High frequency switching Reduce the ripple current Miniaturize the EMC filter by using high frequency carrier 8

9 Relationship between volume and carrier frequency Volume EMC filter Cooling system Carrier frequency Volume of the system Grid LISN EMC filter PWM rectifier Heat sink PWM inverter RL load Stray capacitance Conduction noise measurement system Estimate the conduction noise GaN-FET inverter system with high frequency carrier High frequency noise Large switching loss Smaller EMC filter Larger cooling system Each volume is calculated based on the simulation results Relationship between the carrier frequency and the total volume of GaN-FET inverter system is evaluated 9

10 Relationship between efficiency and power density 96 High efficiency(f carrier =15 khz) High efficiency High power density Efficiency [%] f carrier =15kHz Single stage f carrier =3kHz f carrier =45kHz Three stages Two stages High power density (f carrier =3 khz) High efficiency High power density f carrier =6kHz Power density [kw/dm 3 ] :f carrier =15 khz :f carrier =3 khz EMC filter should be constructed by two stage filter in order to achieve high power density and high efficiency 1

11 MHz band high-frequency power converter Applications Charger Receiver antenna Battery Transmission antenna Generation of plasma Induction heating Wireless power transfer Grid Wireless power transfer HF power source (Target) Transmission antenna 13.56MHz 13.56MHz DC Rectifier Receiver antenna Battery DC load Requirements for HF power source >High frequency >High efficiency >Downsizing 11

12 Conventional method of high-frequency power converter Linear amplifier method Vacuum tube, Power Transistor >Electromagnetic interference (EMI): Low >Efficiency : Low >Cooling system : Large size Switching amplification method Power MOSFET >Efficiency : High >Cooling system : Downsizing Employing wide band gap semiconductors : Silicon carbide(sic), Gallium nitride(gan) >Fast switching, low power loss >Implementation of gate drive unit (GDU) : Complicated >Control gate-source voltage : Difficult Ex) Class A, AB, C, etc 12 npn pnp

13 Concept of the proposed circuit and purpose of this study Concept Simple method Without wide band gap semiconductors, only conventional Si devices are used >Conventional GDU can be used High output frequency over switching frequency Frequency multiplying method is adopted Low switching frequency High efficiency Simple I u V DC 2 S pu S pv S pw S px S py V uo V DC V DC 2 o S nu u S nv v S nw w S nx x S ny y V out 13

14 Proposed circuit Frequency multiplying method - 1. Multiphase inverter with square wave drive using shifted gate signal 2. Multicore transformer is adopted Sum of the inverter output voltage can achieve high output frequency V DC V DC 2 V DC 2 o S pu S nu u S pv S nv 1. Multi-phase inverter Square wave drive v S pw S nw w S px S nx x S py S ny I u y V uo V out 2. Multi-core transformer Primary : Parallel connection Secondary: Series connection U-phase voltage V-phase voltage W-phase voltage X-phase voltage Y-phase voltage Output voltage V DC /2 -V DC /2 V DC /2 -V DC /2 V DC /2 -V DC /2 V DC /2 -V DC /2 V DC /2 -V DC /2 V DC /2 -V DC /2 f out = N*f sw Ex.) f out = 2.5 MHz, N = 5 f out = 5 khz V uo V vo V wo V xo V yo V out 72 deg. T sw /5 72 deg. T sw 72 deg. 72 deg. 14

15 Applying series resonance using resonance capacitance Multi-phase inverter V DC S p p u u S py u 2 v V vo V DC w o S x n y V out V DC 2 n S n n u u u Su ny Leakage inductance V uo V wo V xo Resonance capacitor Sinusoidal voltage V yo A resonance capacitance is connected to the secondary side of multicore transformer Leakage inductance is effectively used for sinusoidal output voltage 15

16 Experimental results (Series resonance, f out =2.5MHz) rms value 6 5 (b) Load voltage Vload [V] (a) R load : 33 W R load : 1 W High output R load : 5 W Resonance capacitance C r [pf] Load voltage and current Almost sinusoidal waveform Output voltage is changed by resonance capacitance value U phase voltage V uo (1V/div) U phase current I u (2A/div) Load voltage V load (1V/div) Output current I out (1A/div) U phase voltage V uo (1V/div) U phase current I u (2A/div) Output voltage V out (1V/div) Output current I out (1A/div) Load resistance: Small Quality factor for resonance: Large > Output voltage: Decreased 4 (ns) (a) R load : 5W (C r :1pF) 4 (ns) (b) R load : 33W (C r :1pF) 16

17 Conclusion Power loss calculation (Semiconductors, passive components) Clarification of design methods Applications High frequency switching Printed circuit board design Volume estimation (Passive components, heat sinks) Combination Wireless power transfer for gate drive supplies of a medium-voltage inverter High power density PWM inverter with wide band-gap devices Frequency multiplying circuit for MHz output frequency etc. 17