Neutral-Point Clamped (NPC), such as diode-clamped, multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. However, the NPC Multilevel topology also has variable type of structure which cannot be found due to lack of systematic derivation methodology. A new system method, called NPC Flow Graph (NPC-FG), is proposed to derive all the possible topologies in this paper, which sets the basic criteria and special steps to construct topologies. Thirty-two NPC five-level topologies have been derived. Among them, a new family of Space NPC (S-NPC) multilevel topologies is also proposed by NPC-FG. Additional topologies can be derived based on different criteria to meet special requirement, such as Photovoltaic (PV) application. The proposed method can find all the existing multi-level NPC topologies, as well as new ones, with better performance.