I. INTRODUCTION
The use of Power Electronics (=PE) converters to improve the power quality in the Medium Voltage (=MV) and Low Voltage (= LV) electrical network is growing both in numbers and power handling capacity, see [1]–[4]. Moreover, in future PE conversion technique will also enter MV power distribution market segments, which today are dominated by mature electromechanical and electromagnetic technology. Therefore, also the economical replacement of a typical power frequency MV/LV distribution transformer in the lower power range (100KW-2MW) with a high frequency (= HF) switched “electronic transformer” and extended functionality seems to be feasible. Besides this application HF switched line-side converters incorporating a HF-transformer can replace the bulky power frequency transformer of trains. This gives an opportunity to reduce the size and weight of the supply system for trains, see [5] and [6]. Figure 1 gives an overview.