Higher Voltage Made Simple
The solar industry has pushed DC link voltages from 1000V to 1500V and this is now becoming common in other markets. Solar-adjacent energy storage systems have batteries capable of operating continuously at high voltage. Electric vehicles and their chargers have increased voltage to decrease charge times. Wind turbines, traditionally 690VAC, are pushing line voltages beyond 1000VAC.
These applications have all taken advantage of multi-level topologies — previously academic research topics — which are now mainstream. In particular, the neutral point clamped (NPC) topology popular for solar inverters has given way to the active neutral point clamped (ANPC) topology. This topology can operate efficiently at both positive and negative power factor — a requirement for efficient battery energy storage systems. This topology can easily be constructed from high-power half-bridges such as the SEMiX 3 Press-Fit. The terminal layout of these modules also facilitates paralleling for high-power converters.
With the new availability of 2kV-class silicon carbide, it is possible to move back to 2-level converters in some cases. The latest generation SiC MOSFETs allow for switching at the same equivalent frequency as the 3-level converter. The reduction of switches and associated driers reduces overall system complexity. The SEMITRANS 20 can be equipped with 2kV SiC to build MW-class converters at a fraction of the physical size of a 3-level topology. When used in battery energy storage applications, this device also offers higher efficiency than the equivalent ANPC design.