Advantages of NPC inverter topologies with power modules

The technology leaders are inverter applications in the solar market, but also uninterruptible power supplies and motor drives have new targets for improved efficiency.

Vincotech’s article about Neutral Point Clamped (NPC) Technologies shows alternatives for 3~ inverters with 700V DC-link voltage. The NPC topology offers advantages such as reduced switching losses, smaller output current ripple, and total +/- supply voltage is split. Only half of the voltage has to be switched, and this also cuts the switching losses in the transistor by half. In the shown NPC topology, it is possible to use 600V components instead of 1200V types. On top of that, in the 600V technology much faster components are available than in 1200V. This will lead to further reduction of the switching losses. The Neutral Point Clamped topology will have lower ripple in the output current and half of the output voltage transient. This will reduce the effort for filtering and isolation in the filter inductor. The DC voltage is divided into a positive and negative voltage, which supports the serial connection of DC capacitors without the need for leakage current compensation.

This article about the NPC Technologies provides a comparison of two different 3-level topologies and a standard 3-phase bridge. It will show that neutral point clamped technologies, which are even more cost effective, can achieve an efficiency of 98.04% compared to 96.65% of the standard 3-phase bridge.