Active front end converter based on MMC

Modular multilevel converter (MMC)

Modular Multilevel Converters (MMCs) are a key technology in driving the energy transition of our society, providing improved efficiency, power quality, fault-tolerance and higher power density. The ability to operate in different voltage ranges makes such technology essential for the development of both AC and DC grids. By leveraging the capabilities of MMC technology, we can shape the energy systems for a sustainable future.  

Due to the lack of current standards to medium-voltage DC grids, a provision of inter-connectivity for different voltage levels is essential to enable the realization of next generation hybrid grids. Currently, power electronic converters are predominantly utilized in a limited range of medium-voltage of applications, typically below 10 kV, using legacy 2-or3-level solutions. 

Our portfolio

  • Topologies specifically trimmed for battery interfacing
  • Si-, SiC-, and GaN-based circuit development
  • Low parasitic magnetics design (planar and conventional)
  • Low parasitic active circuit design

Our offer

  • Multi-port power converters
  • Partial power processing for ultra-high efficiency and density
  • Multi-bus MVDC power converter
  • Low parasitic magnetics and active circuits design

Applications fields

  • Automotive industry
  • Renewables
  • Battery integration on the grid
  • Consumer electronics


MMC technology is crucial for medium-voltage range hybrid grids. Despite the requirement for a large number of power electronic devices, ensuring a highly reliable converter is essential to enable uninterrupted operation and reduced maintenance time. Fraunhofer ISIT offers the following benefits:

  • High efficiency step-down operation: enhance inter-connectivity to hybrid grids
  • DC fault ride-trough: ensure grid stability during faults 
  • Innovative overcurrent management to support AC grids
  • Well-equipped medium-voltage laboratory for tests up to 10 kV – 1 MVA with flexible multiple low-voltage and medium-voltage MMC setups.


Multiport partial power processing converter

Converter with energy storage integration for EV stationary charging

Offshore Wind Farms

  • High power transfer capability
  • Low power losses for high distances
  • Independent control of active and reactive power


  • Fast dynamics for voltage regulation
  • Low harmonic distortion
  • High efficiency for hot-standby solutions

Fast Charging stations

  • High controllability
  • Integration of energy storage units
  • High power density and efficiency

MVDC Distribution

  • Improved connectivity
  • Increases power capacity by up to 80% compared to AC
  • Power flow control
  • High flexibility

  • Investigation of the external connection mechanism for measuring the voltage drop of power semiconductors during operation.
  • Evaluation of different modulations in the MMC and their effects on the DC-side current and on the wiring of the converter.
  • Investigation of protection strategies using the device's temperature inference based on its TSEP.
  • Development of a methodology that correlates device temperature and circulating current.