Fundamental Switching Frequency Pulse Width Modulation of Nine-Level Current-fed Multilevel Converter for Solar Application

The aim of this paper is to develop a real-time computational method that determines switching angles of selective harmonic elimination (SHE) for operating nine-level (9L) current-fed multilevel converter(MLC). The computation algorithm for SHE conventionally requires huge calculation time to identify switching angles of the inverter and hence a truth table based modulation is applied for operating the converter in real-time. To overcome this, a new analytical method has been proposed in this paper that minimizes the computation time to calculate the switching angles. However, these switching angles cannot be directly applied to current-fed MLCs. Unlike voltage fed converters, the current-fed converters have additional operational constraints on the modulation technique. Hence in this paper, a conversion technique has been utilized to convert the un-constraint SHE angles into constraint angles in order to operate current-fed MLCs. A low power prototype of 9L current source inverter has been set-up to experiment and validate the proposed real-time calculation method at the fundamental frequency of 50Hz.