2.1 Multilevel Diode ClampedAccording to patents the rst multilevel inverter (MLI) was designed in 1975 and it was
a cascade inverter (cascaded inverters will be presented in a later chapter) with diodes
blocking the source. This inverter was later derived into the Diode Clamped Multilevel
Inverter, also called Neutral-Point Clamped Inverter (NPC) [2], see Figure 2.1. This
topology is, as can be seen from the gure, based of the same principal as the before
mentioned three-level inverter in Figure 1.4.