Allow for high power density, high temperature, harsh environment operation (Datta) The following chart summarizes the needs that various potential application spaces have for high current, high performance cost competitive modules: kVA V A IGBT Volt SiC Volt Benefits Wind Doubly-fed Induction Gen 750 690 1331 1700V 1700V Higher efficiency Higher switching frequency (Fsw: 5-->20kHz) Better fault handling Synchronous Gen 3000 960 3827 1700V 1700V Solar Single Stage 1000 480 2552 1200V /1700V 1700V SiC Higher efficiency Higher switching frequency (Fsw: 5-->20kHz) Better fault handling Traction 1000 1500 816 2500V 2500V Higher Power Density Healthcare MR 1000 1000 1000 1200V 1200V/ 2500V Very High switching frequency (Fsw: 20kHZ-->60kHz) Higher Power Density MV Drives 3L 2500 3300 928 4500V 1700V/ 2500V Series Higher Power Density Higher switching frequency (Fsw: 1-->10kHz) Cascade 417 953 928 1200V 1200V 3L 5000 6600 928 4500V series 1700V/ 2500V series Cascade 556 1270 928 1200V 1700V (Datta) The use of SiC in place of Si in power electronics devices was discussed by John Amy based on a 2007 paper that he co-authored. These include: bridge bridge
MV semiconductors => high losses =>limits switching frequency & power throughput & grid harmonics MV => high energy => limits size of passives=> shorter time constant =>dynamic operation, requires fast action These MV drives are challenged by: Low switching frequency => low control bandwidth => difficult to meet control objectives High losses => Limits power throughput (Arshad) High power can be achieved by increasing the voltage. The Advantages and Disadvantages of increasing voltage are: Disadvantages Advantages . High dv/dt More complex insulation concept Smaller cross sectional area of cable - Cost effective drive set-up- Less familiarity of plant electricians and drive service personnel with medium voltage levels Circuit breakers of lower current rating effective drive setup Lower rms current, lower conduction losses Higher efficiency (Arshad) Benefits of SiC to drives include: SiC switching losses are very flat with switching frequency: Higher output power compared to Si at f_sw = const. Crossover point above critical switching frequency (LV) Si: P_losses = P_cond + P_sw (40%) (60%) SiC: P_losses=P_cond + P_sw (60%) (40%) (Arshad) For MV drives SiC Diode technology brings a definite benefit in reducing the turn-on switching losses of the semiconductor switch. ABB see the hybrid Si+SiC power modules as a promising entry point for SiC in MW applications, but limited by the Si operating temperature Full SiC modules show an additional reduction in losses compared to hybrid technology, but are limited mainly by their low current rating and over voltages due to the fast unipolar SiC switch (Arshad) Aii.b. Manufacturers Challenges A long list of items were identified that required additional R&D work to resolve.
Written Responses - 11 John Amy - Navy The Navy answer is 2-4 years. Subhashish Bhattacharya – North Carolina State University Less than 2-3 years Roger Cooley – Northrup Grumman Efficiency numbers are believed more than “payback period” Geoffrey Dolan – Google This seems too application specific. The goal should be reduction in overall system cost at installation. Small premiums may be supported for efficiency but goal for mass adoption should be lower installed system cost. Krstic Slobodan –Eaton Corporation 1-2 years Stephen Kuznetsov – Raytheon 3 year payback essential Veli-Matti Leppanen – ABB Maybe there could be incentives via some sort of leasing arrangements -the savings could be split between equipment provider and end user. Tim McCoy – McCoy Consulting 3 years or less for commercial applications John Shegirian – General Dynamics 3 years Brij N. Singh - John Deere Inc. Increased efficiency and increased performance offered with medium and high voltage inverter could result into a realistic payback period of two to three years. If there are additional advantages such as reduced size and improved fuel economy in case of transportation applications for heavy-duty vehicle could be a good customer pull to generate strong market interest. Ajith Wijenayake – DRS Preferably less than five years (similar to typical payback periods in the commercial drive industry) but may be different for different applications and should consider individual applications. Key Question 1c. What are efficiency benefits that would warrant incentives?
Written responses - 9 John Amy- Navy A VSD with an efficiency of ≥98% would assuage concerns about increased losses. Just as important is the partial load efficiencies; is there an efficiency drop-off at light load conditions? Does the VSD reduce the overall system energy consumption? Rajib Datta – GE Really depends on application. Most applications are not efficiency sensitive. Secondary benefit of loss and thermal management may be more critical. Geoffrey Dolan – Google Industry on island grids could be early adopters –high cost of electricity Bill Geiwont-Vacon Agency & Utility regulations have always lead the need for improved control methods and overall system efficiencies. I look to these policy makers to indirectly push customers into replacing the old soft starters with VSDs to reduce energy consumption and in the case of grid connected generating systems that the AFE will need to play system stabilizer requiring higher bandwidth control systems. While a typical Si based VSD can quickly meet the energy savings goals I believe SiC will be needed, with its higher switching frequency for grid stability control . Krstic Slobodan –Eaton Corporation Efficiency of drive is not critical. Process efficiency benefits from drive and determines the need. Stephen Kuznetsov – Raytheon Efficiency not important as reliability/MTBF. Efficiencies of 96-97% are realistic goals Veli-Matti Leppanen – ABB Maybe there could be incentives via some sort of leasing arrangements-the savings could be split between equipment provider and end user. Tim McCoy – McCoy Consulting Efficiency benefits relative to what? Si-based VSD’s or direct drive motor applications? Brij N. Singh - John Deere Inc. As compared to Silicon inverter if WBG (read SiC) inverter offer additional 10% to 15% efficiency, it would be a significant incentive for customers of this new technology . Ajith Wijenayake – DRS Elimination of bulky magnetic MV transformer by a HF transformer is a definite benefit in terms of size and efficiency, but at a higher cost in the short term.
Written responses - 9 John Amy- Navy The Navy perspective: (1) Demonstrate reduced losses (not the same as converter efficiencies) (2) Demonstrate high frequency (higher than Si) wave forms. Subhashish Bhattacharya – North Carolina State University Performance in terms of current/torque control Roger Cooley – Northrup Grumman Increased Fgas to reduce size and cost of passives Rajib Datta – GE Power density which should translate to system level cost saving. Dave Grider – Cree What are requirements of HV SiC Devices and Modules ( 10 kV-15 kV SiC MOSFET, ≥15 kV SiC IGBT) in terms of short circuit capability, SOA (RBSOA, FBSOA), Current, Voltage, Switching Frequency, Thermal Cycling, Operating Temperature Stephen Kuznetsov – Raytheon (1)Slew rate of VSD in going from full-speed forward to full-speed reverse is an essential and limiting performance characteristic for a bidirectional drive. (2)Ability of a VSD to ride thru a load short-circuit without damage. Tim McCoy – McCoy Consulting Depends on specifics of application. Could be – frequency, efficiency, high temperature, size/weight Brij N. Singh - John Deere Inc. WBG VSD should operate at higher voltage, temperature and switching frequencies as compared to Silicon VSDs. John Shegirian – General Dynamics Reduced cooling and filtering requirements. Elimination of input transformers. Question 3a. What additional technology and advanced device performance are needed for HMW VSD’s (for example, which SiC or Si devices type/voltages, etc. would be most beneficial)? Written responses - 12 John Amy- Navy