Soft switching three level inverter (S3L inverter)

The Soft Switching Three Level Inverter - abbreviated to S3L Inverter - was first introduced in 2011. It is a novel circuit topology for PWM inverters, whose areas of application include electrical drives and grid-tie inverters for photovoltaic installations and wind power plants, and for power supplies. It is of very simple design and therefore inexpensive. It is implemented completely as soft switching and hence offers very low switching losses. This means that its efficiency is very high, and it can achieve very high values for the switching frequency. This paper begins by describing how the device functions. It then goes on to discuss specialised methods of control. A variant of the S3L Inverter with a deactivatable snubber circuit is presented. A quantitative comparison between a well-known hard switching NPC 3-level inverter and the novel S3L Inverter using 90 kVA (three-phase) prototypes illustrates the advantages of the S3L inverter.