Performance Characteristics of a Cascaded Two-level Converter

A cascaded two-level power converter is proposed which utilizes two six-transistor inverters and is capable of producing voltages which are identical to those of three-level and four-level converters. Since the machine voltages are the same, the converter performance is the same as is verified through laboratory tests. The advantages and disadvantages of the proposed cascaded converter are explored. The proposed converter is simpler to construct and offers more nonredundant switching states per number of active semiconductors than standard multi-level converter

Harmonic Distortion Optimization of Cascaded H-Bridge Inverters Considering Device Voltage Drops and Noninteger DC Voltage Ratios

This paper considers achieving the minimum total harmonic distortion (THD) or frequency-weighted THD (WTHD) of the staircase-modulated output voltage of single-phase multilevel inverters, with or without elimination of the lowest order harmonics. The minimal THD values, together with the corresponding step angles and dc voltage source ratios, have been obtained for the 5-, 7-, 9-, 11-, and 13-level cases; accounting for the device voltage drops when the load is resistive or is moderately inductive is described. Similarly, the minimal WTHD values, together with the corresponding step angles and dc source voltage ratios, have been obtained for the five-, seven-, and nine-level waveform cases. The results show that requiring harmonic elimination leads to larger W/THD than the minimum W/THD that can be achieved without this requirement. Furthermore, a 13-level waveform is needed to attain a voltage THD less than 5%, and a nine-level waveform is needed to attain a WTHD less than 0.5%. Experimental measurements are presented as verification of the analytical results

Energy harvesting from vibration with alternate scavenging circuitry and tapered cantilever beam

Piezoelectric transducers are increasingly being used to harvest energy from environmental vibrations in order to either power remote sensors or charge batteries that power the sensors. In this paper, a new voltage compensation scheme for high-voltage-based (\u3e 100 V ) energy harvesting is introduced, and its fundamental concepts, as well as the operation details, are elaborated. This scheme, when applied to the voltage inversion method [synchronized switch harvesting on inductor (SSHI)], provides an increase of over 14% in harvested power when compared to the parallel inversion method (parallel SSHI) alone and more than 50% in the case of series inversion method (series SSHI). Second, tapered cantilever beams were shown to be more effective in generating a uniform strain profile over rectangular and trapezoidal beams if they are precisely shaped, resulting in a significant increase in harvested power over available methods in the literature from laboratory experimental tests. In addition, a simplified method to design such a beam is introduced. Finally, a field test of the proposed tapered beam is conducted by using a dozer for earth-moving applications, and experimental results are discussed. © 2006 IEEE