Inverters

Development and prototype manufacturing of application-specific inverter power electronics

Electronics devices based on wide bandgap semiconductors (WBG), such as SiC and GaN transistors, allow inverter systems to achieve outstanding efficiencies, power densities and switching frequencies that significantly exceed the current state of the art. In order to realize the combination of highest output powers and currents with maximized switching speeds (> 20 kV/µs) in automotive and aerospace applications, a specifically tailored design of the commutation cell, the power module and the gate drive is necessary. At Fraunhofer IISB, we develop customized SiC and GaN inverters based on electrical and thermal simulations, supplemented by experimental test setups.  

• Voltage range for typical automotive applications: 48 V to 850 V (and beyond)
• Output power up to 1 MW
• Focus on silicon carbide (SiC) and galium nitride (GaN) based inverter systems
• Expertise in a variety of inverter topologies (Multilevel, Multiphase, etc.)
• Application-oriented motor control software development for various types of electrical machines
• In-house testing facilities with several motor test benches and a vehicle test bench

Areas of application: Traction, fuel cell air supply, electric turbochargers, highly integrated drives

Design, development, assembly and characterization of 3-level inverter systems

Realization of technology demonstrators for various 3-level topologies:

• NPC (Neutral Point Clamped) GaN-based 800 V converter
  
• T-type silicon carbide (SiC) inverter
• ANPC (Active Neutral Point Clamped) power module characterization
  

We develop SiC- or GaN-based inverters including motor control software for high-speed motors (e.g. compressors, fuel cell air compressors or electric turbochargers). These require the highest output frequencies on the inverter and therefore also high switching frequencies in order to avoid additional losses and torque carry-over in the machine. Wide bandgap semiconductors (WBG) are particularly suitable for use in these applications.

Typical requirements:

• Nominal DC link voltage: 450 V and 850 V
• Output power: 10 to 80 kW
• 2- or 3-level topologies
• Max. Switching frequency: 80-100 kHz
• Sensorless motor control

Fraunhofer IISB is cooperating with the Control Engineering Laboratory of the Faculty of Electrical Engineering, Precision Engineering and Information Technology (efi) at Technische Hochschule Nürnberg Georg Simon Ohm in the development and analysis of modular control algorithms for the following machine types:

• Permanently excited synchronous machines (Permanent Magnet Synchronous Motors PMSM)
• Asynchronous machines (Induction Motors, IM)
• Externally excited synchronous machines (Electrically Excited Synchronous Motor, EESM)
• Brushless DC machines (BLDC)
• Mehrphasige und 3-Level Topologien

Based on our R&D activities, we offer the following solutions:

• Conventional drive control methods (e.g. field-oriented control)
• Adaptive control of drive systems (e.g. iterative learning control)
• Sensorless control and high-frequency control algorithms, e.g. for high-speed drives (electric turbochargers, fuel cell air compressors, etc.)
• Implementation and testing on self-developed control board hardware
• Test of the developed drive controls on the in-house motor test bench

Simulative and experimental studies on drive converter-specific issues

Research projects provide the ideal framework for collaborations on new ideas and developments. Examples of typical topics are:

• Packaging space and integration studies
• Inverter topology or potential studies
• Power module characterization
• Simulative or experimental thermal studies (e.g. heat dissipation from power modules, DC link capacitors, etc.)