Comparison of Hard-Switched Multi-Level Inverter Topologies for STATCOM by Loss-Implemented Simulation and Cost Estimation

The voltage rating of commercial high-power IGBT modules is not sufficient for most medium-voltage applications. Therefore, three types of multi-level inverters have been proposed as a solution. They are the diode clamp multi-level inverter (DCMLI), the flying capacitor multi-level inverter (FCMLI) and the cascade cell multi-level inverter (CCMLI). In this paper, these three types of multi-level inverters are designed for a 6.6 kV STATCOM. The aim of this paper is to choose the best topology by comparison of operational losses and costs. In the beginning, the advantages and disadvantages of three multi-level inverters are explained. Then operational losses calculated by using a new simulation tool are compared. This tool calculates actual operational losses from a circuit simulation with ideal switches and measured loss data. Finally, the costs of inverter units, inverter cabinets and capacitor banks are estimated and compared