S3L-Inverter: Switching-loss-free 3-level pulse-controlled inverter with snubber circuit

The new Soft Switching Three Level Inverter (S3L–Inverter) is of striking simplicity and is therefore inexpensive. Because of the underlying principle, it works without losses and thus with maximum efficiency. The inverter is easily controlled, has EMC friendly inherent di/dt and du/dt limitation, and can be built using low-cost standard semiconductors.

Pulse width modulation inverters with ever higher switching frequencies and simultaneously increased efficiency are often being sought. Examples of such applications are electric drives in a variety of fields, such as ultra-light and high rpm drives in the aerospace industry and in hybrid cars, but also solar and wind power inverters as well as uninterruptible power supplies.

To meet these expectations, it is necessary to develop new switching topologies.  A known approach is to use multi-level inverters which nowadays represent the current technology.  A further approach is the „soft switching“ technology which seeks to eliminate switching losses via resonant, quasi-resonant, or passively switching losses reducing topologies resulting in higher switching frequencies and improved efficiencies.

At the Laboratory for Power Electronics of the HTWG Konstanz, these two approaches have been successfully combined in a simple manner and with unique characteristics.
The new Soft Switching Three Level Inverter (S3L-Inverter) is of striking simplicity and is therefore inexpensive. Because of the underlying principle, it works without losses and thus with maximum efficiency. The inverter is easily controlled, has EMC friendly inherent di/dt and du/dt limitation, and can be built using low-cost standard semiconductors.

• Free of switching losses due to its design / thus maximum efficiency (one phase or three phases)
• Low heat generation
• Small cooling elements and fans
• Very high switching frequencies possible
• Smaller and lighter smoothing inductors and capacitors
• Excellent EMC (Electromagnetic Compatibility) characteristics
• di/dt and du/dt limiting
• Integrated du/dt filter
• Use of low-cost standard semiconductors / IGBT, GTO, IGCT

• Electric Drives
• Solar Power Inverter
• Wind Power Inverter
• Uninterruptible Power Supplies (UPS)
• HVDC