current source inverters (CSI). The second group consists of alternative topologies of
direct frequency converters. These topologies have no DC energy storage elements
and basically consist of an array of static power switches connected between the
source and load terminals. For good performance direct frequency converters have
small capacitors and inductors, such as high frequency component filters or small
regenerative AC energy storage. The last group is a combination of direct frequency
converters with small-sized local DC energy storage elements or an additional module
with a DC–DC boost converter.