Cree PV Inverter Tops 1kW/kg with All-SiC Design

Cree PV Inverter Tops 1kW/kg with All-SiC Design Alejandro Esquivel September, 2014

Presentation Outline 1. Meeting an Industry Need a) 1kW/Kg b) No electrolytic capacitors in DC link 2. 50 + kw SiC based PV Inverter Design a) Boost Stage b) Inverter Stage c) Auxiliary Power Supply 3. Performance Comparison Copyright 2013 Cree, Inc. 2

Cree SiC Power Portfolio Products and Support SiC Schottky Diodes: 600V, 650V, 1200V, 1700V 1A to 50A Packaged and bare die Reference Designs: Solar - Boost and Inverter SMPS - PFC, ZVS, Flyback Package Styles: TO-220 TO-247 Full-PAK DPAK (TO-252) D2PAK (TO-263) QFN Isolated TO-220 Bare die for power modules C2M SiC MOSFETs: 1200V, 1700V 1Ω to 25mΩ (4A to 60A) Packaged and bare die SiC Power Modules: 1200V, 1700V 100A to 300A Half-bridges 50A Six-pack Gate Drivers: Single and dual Cree designed Partnered designs Copyright 2014, Cree, Inc. pg. 3

Commercial PV installation 100kW 1 MW Commercial three-phase roof top system Need for: Small size Light weight High power density Lower installed system cost SiC devices enable the best solution to achieve this need Power density needed > 1 kw/kg 4

What Is Used Today - Example Kaco Blueplanet 50.0 TL3 50 kw, TL3 series Full Power MPPT Voltage Range Operating MPPT Voltage Range 480 850 VDC 200 850 VDC No. Independent MPPT Input 1 Nominal output power 50 kw CEC Efficiency 97.5% Peak Efficiency 98.3% Power Factor > 0.99 Output Voltage Operating Temperature Range Cooling Weight Isolation Transformer Volume 480 Vac -30 C to 60 C (de-rated > 45 C) Forced convection 173 kg No 840 355 1360 mm Power density = 0.29 kw/kg Need: Increase this value > 3 Cree SiC Technology can achieve this 5

Cree SiC Technology Enables ½ Volume and <1/3 Weight Cree SiC based 3-ph, PV String Inverter comparison Full Power MPPT Voltage Range Operating Voltage Range 480 850 VDC 450 800 VDC 200 850 VDC 400 950 VDC No. Indep MPPT Input 1 2 Nominal output power 50 kw 50 kw CEC Efficiency 97.5% 97.8% Peak Efficiency 98.3% 98.7% Power Factor > 0.99 > 0.99 Output Voltage 480 Vac 480 Vac Operating Temperature Range -30 C to 60 C (de-rated > 45 C) -30 C to 60 C (no de-rating) Cooling Forced air Forced air Weight 173 kg 50 kg Isolation Transformer No No Volume (m 3 ) 0.41 840 x 355 x 1360 mm 0.21 700 x 300 x 1000 mm SiC based 3-ph PV string Inverter Power Density = 1 kw/kg 6

LC line Filter 480 Vac rms l-l Cree All-SiC PV Inverter Reference Design Overview Aux. Power Supply Aux. Power Supply 450 to 800 VDC 2x MPPT channels Driver Driver 825 VDC Channel A Channel B Scalable to any numbers of MPPT channels ~ MPPT Boost, 75kHz 3-ph Inverter, 48kHz Control Plane 7

Power Stage Efficiency 3LT-Type Inverter Chosen for High Frequency Efficiency 100.0% 2L Si 3L-NPC Si 3L-T Si 2L SiC 3L-T SiC 2L 99.5% 99.0% 98.5% 3L-NPC 98.0% 97.5% 97.0% 96.5% 3L-T 96.0% 0 5 10 15 20 25 30 35 40 45 50 Switching Swithcing Frequency (khz) 8

Inverter Schematic: All SiC Active Power Semiconductors Input Filter 4-ph interleaved Boost Converter DC Link 3-ph T-Type Inverter Output Filter 2x C2M0080120D, SiC MOSFET in parallel per phase leg. 10x 700uF 600VDC film 2x C2M0025120D, SiC MOSFET in parallel per phase leg upper and lower switch. 3x 4uF, 470Vac film 3x 230uH, metglas core 2x C4D10120D, SiC MPS diodes in parallel per phase leg. 1x C2M0025120D, SiC MOSFET per T-leg. 1x C5D50065D, SiC MPS Diode per T-leg. 9

50kW 4-Channel Boost Front End EMI Filter Choke Boost Chokes* 2pcs C2M0080120D per each phase MPPT Ch A Controller MPPT Ch B Phase Gate driver 10

3-Level, T-Type Inverter Topology 3500 µf 270 µh Main lower & upper MOSFET position: 2x Cree 1.2kV SiC Mosfet, 50A, 25 mohms Uses Cree SiC MOSFET body diode in main anti-parallel with main power switches T-Branch MOSFET position: 1x Cree 1.2kV SiC Mosfet, 50A, 25 mohms T-branch Diode position: 2x Cree 650V, 50A, C3D50065D 11

SiC System Efficiency v/s Si based system* Better Overall efficiency @ 1/3 rd the weight CEC Efficiency: Kaco 97.5% Cree 97.8% * Independent test data for KACO BluePlanet 50.0 TL3 provided by gosolarcalifornia.ca.gov 12

Thermal Images of Boost With 400V In /800V Out at Full Load C2D0080120D C4D10120D Boost Inductor Part Tc ( C) Part #1 Tc ( C) Part #2* C2M0080120D 92.6 94.4 C4D10120D 67.5 64.9 Boost Inductor 69.7 * Note excellent sharing between paralleled devices. Note: Testing is based on full load operation after 30min with fan to cool system Ambient temperature = 25ºC 13

Operating Temperature Data Vin = 600 / 700VDC Tamb = 22ºC Po = 48 kw LC output filter T core = 66 (with potting) 103ºC (no potting) T core = 38/35ºC T c = 54/53ºC T c = 70//68ºC T c = 39/38ºC T c = 61/54ºC T c = 46/42ºC 14

60W SiC Based Auxiliary Power Supply Cree 60W Single-end Flyback reference similar to that used in 50kW: Input voltage: Wide input range 200Vdc to 1000Vdc Output voltage: 12Vdc/4.5A; 5V/0.5A; -12Vdc/0.25A Operating frequency: 75KHZ Cree 1700V SiC MOSFET: C2M1000170D PQ2625 transformer Cree 60W Aux Power Demo board with 1700V SiC MOSFET Cree 1700V, 1Ω MOSFET: Higher blocking than available silicon Higher efficiency for cooler operation Enables higher reliability than comparable silicon designs pg. 15

All SiC 50kW PV String Inverter Test Assembly Boost converter DC Link Film Capacitors 2x 3.5mF, 1.1kV Controller Output Power = 47.8kW Output Voltage = 492 Vac l-l rms Output Current = 56A rms DC link Voltage = 850 VDC 3-phase, balanced resistive load Output filter Inverter Power stage 16

50kW Physical Specifications All aluminum enclosure 30cm 100cm Weight distribution shown in Kg Total weight = 50 Kg 70cm 17

Summary Using SiC MOSFETs available today from Cree enables up to 3x the power to weight ratio when compared to current Si based systems. Higher F sw reduces cost of the magnetics in the boost and output filter while delivering improved efficiency compared to Si solutions. Installing smaller, lighter inverters will lower installation costs. Less parts and the use of film capacitors in the DC link can improve reliability of the system. Cree is developing a complete range of SiC discrete and module devices to support the power conversion market. SiC makes economic sense today! 18

50 kw PV inverter impact of C2M FETs C2M0025120D MOSFET Decreased BOM cost Size, weight reduced Efficiency improved Reference: See Cree booth. Size Weight Inverter BOM Inverter install cost $/kw savings 50% 60% 30% 50% 3-4% Copyright 2014, Cree, Inc. 19