A soft-switching three-level inverter (S3L inverter) is a high-efficiency power electronic

inverter A power inverter, inverter, or invertor is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed. Inverters do the op ...

intended, in particular, for use with three-phase drives, as a

grid-tie inverter A grid-tie inverter converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid, at the same voltage and frequency of that power grid. Grid-tie inverters are used between local electrical ...

for

photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...

installations or

wind turbines A wind turbine is a device that converts the kinetic energy of wind into electrical energy. , hundreds of thousands of large turbines, in installations known as wind farms, were generating over 650 gigawatts of power, with 60 GW added each y ...

and in

power supplies A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

. The topology was developed in 2009 at HTWG Konstanz (Constance University of Applied Sciences).

Operating principle

Inverters are used for converting DC voltage into AC voltage. Their construction typically makes use of

power transistor A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics (for example in a switch-mode power supply). Such a device is also called a power device or, when used in an integrated circuit, a power IC. ...

s and

diode A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance ...

s. These are operated as electronic switches. In conventional designs using "hard" switching, this gives rise to Peter R. W. Martin (editor): Applikationshandbuch IGBT- und MOSFET-Leistungsmodule. ISLE Verlag, 1998, , Section 1.2.3 Qualitatives Schaltverhalten von MOSFET und IGBT beim harten Schalten (PDF version). which, especially for high values of the switching frequency, cause a reduction in their

energy conversion efficiency Energy conversion efficiency (''η'') is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radi ...

. To improve their efficiency, high-power inverters (from about 10 kW) frequently make use of a technique referred to as a three-level design ( three-level inverter).Akira Nabae, Isao Takahashi, Hirofumi Akagi: A New Neutral-Point-Clamped PWM Inverter. In: IEEE Transactions on Industry Applications. IA-17, No. 5, 1981, pp. 518–523, doi:10.1109/TIA.1981.4503992. Forming the basis of the S3L inverter is a hard-switching three-level inverter of this kind with a T-type topology.M. Schweizer, J. W. Kolar: High efficiency drive system with 3-level T-type inverter. In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011). 2011, , pp. 1–10. This base design is supplemented by a snubber circuit consisting of a few passive components.M. W. Gekeler: Soft switching three level inverter with passive snubber circuit (S3L inverter). In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011). 2011, , pp. 1–10. It prevents the occurrence of simultaneously high values of voltage and current, and hence high power dissipation values, during the switching process. All switching processes therefore take place in a "soft" manner. In this way switching losses are largely avoided. Furthermore, because the snubber circuit functions, in principle, without losses, the conversion efficiency of the inverter remains high even for high values of the switching frequency.Manfred W. Gekeler: Weich schaltender 3-Stufen-Pulswechselrichter mit verlustfreiem Entlastungsnetzwerk. In: International ETG Congress 2011 (ETG Technical Report 130 Part B). 2011, , pp. 264-270.3-Level Pulse Width Modulation Inverter with Snubber Circuit; US Patent No. US 8,462,524 B2; Date of Patent: Jun. 11, 2013; Inventor: Manfred W. Gekeler, Constance (DE); Assignee: Hochschule Konstanz, Constance (DE)

References

{{reflist Electrical power control