How to Select the System Voltage of MV Drives—A Comparison of Semiconductor Expenses

The application of a particular medium-voltage converter in a certain application depends on numerous criteria. However, in completely new installations, the choice of the system voltage is very often uninhibited of external constraints. Then, the voltage level shall be selected to enable the most efficient power conversion at the lowest cost. This paper is dedicated to help in finding the best voltage level for three-level neutral-point-clamped voltage source converters (3L-NPC VSCs) with respect to the power semiconductor devices. Three insulated-gate-bipolar-transistor-based 3L-NPC VSCs of different voltage levels (2.3, 3.3, and 4.16 kV) are investigated and compared regarding their maximum output power, semiconductor efficiency, and semiconductor cost per MVA output power. The effects of thermal cycling, the loss distribution within the converter, and switching frequencies from 300 to 1050 Hz are considered in the evaluation.