Towards lossless electrical energy converters

forthcoming

"Electrical energy is typically converted four times between source and load, by over 100.000 GW installed converters. Over 99% efficiency is already reality, e.g., in PV inverters, however in a trade-off with power-density and complexity. Thus, most converters stay below the technical performance limits. Incremental advances in semiconductor technology will continuously push these limits’ values, but does not fundamentally change it. This project takes a disruptive approach, investigating partial-power-processing (PPP): Recently, we operated a 99%-efficient 2-level half-bridge in a multilevel topology, increasing the external capacitive-load charging voltage and power 6-times, while keeping the inner losses almost constant. From 2 to 7 level operation monotonically improved the system efficiency from 99% to over 99.7%. A global maximum was not yet reached. PPP theoretically reduces the losses by a factor of N, if only 1/N of the power is converted by a lossy converter while most power is delivered directly to the load by almost-lossless bypass switches from energy buffers. The question is: ""How can electrical conversion efficiency be further increased with partial-power-processing, targeting 99.9% for selected loads?” To approach this “lossless” energy conversion, we will (1) theoretically further investigate PPP and many-level converter topologies, semiconductor devices, and operation parameters, (2) design and characterize converters with two cascaded stages of internally already PPP converter-submodules in a novel way to further improve the system efficiency 3 times (to 99.9%). We will investigate (3) low-voltage (< 100 V), medium-voltage (< 1000 V) and high-voltage (< 10 kV) PPP converters, and cascade them to multiply their benefits. (4) Application to selected, initially capacitive-load applications (electrocaloric heat-pump, pyroelectric harvester, dielectric actuators). The project will push electrical energy conversion further towards the “lossless” limit."