A second type of AC source is the micro-turbine generator(MTG). Micro-turbines were developed by the industry throughimprovements in auxiliary power units. The majority of commercialdevices presently available use natural gas as the primary fuel, butthey are free to use other fuels: gasoline, diesel, kerosene, naphtha,alcohol, propane, methane or digester gas. A MTG unit is usuallya high-speed rotating machine (up to 120 krpm). MTGs have therated power from 30 to a few hundreds of kilowatts, generatingelectricity in AC with output frequency from 400 Hz and up to sev-eral kHz. The most common power converter topology that is usedfor connecting micro-turbines to the grid is the frequency converterwith DC-link. Preliminary results of the application of MTGs usingMC (Fig. 10a) demonstrated the ability of the MC to deliver a higherquality voltage to the load in comparison to conventional frequencyconverters