Comparison of Five-Level Voltage-Source Inverter Based STATCOMs

This paper studies the utilization of multilevel inverters in Flexible AC Transmission Systems controllers and, in particular, as static synchronous compensators (STATCOMs). Three different STATCOM technologies based on five-level inverters, namely diode-clamped (or neutral-point clamped), cascaded and hybrid multilevel inverter, are examined and compared. Along with the circuit-level comparison also the compensation performance and power losses are investigated by means of computer simulations. The operation of the STATCOMs is simulated in different load conditions and also measurement data taken from an electric arc furnace is simulated. The results of the comparison show that the differences in the main circuit layouts affect the power loss distribution and the usability of the compensators for unbalanced load compensation.