Common Mode Voltage Suppression for Three-Level Neutral Point-Clamped Inverters

The three-phase neutral point-clamped (NPC) three-level inverter is widely employed in renewable energy power systems due to its low voltage stress on switching devices, low harmonic, and high efficiency. However, the common mode voltage (CMV) issue is a concern. To address the CMV issue, modulation should be enhanced in combination with advanced control and topological innovation. Hence, this paper explores the modulation schemes for NPC inverters to reduce or eliminate CMV. Additionally, three operation modes (i.e., synchronous, interleaving, and integrated modes) for parallel NPC inverters are discussed. The effectiveness of CMV suppression and harmonic characteristics of the explored modulation schemes and operation modes are compared and analyzed through simulations.