DC-AC conversion strategy optimized for battery or fuel-cell-supplied AC motor drives

A novel DC-AC conversion strategy is presented, which is proposing outstanding performances in DC-supplied AC motor drives. Theoretical power system design analyses and wide experimental verifications suggested the adoption of regulated H-bridge boost DC-DC converter stage improving overall cost and efficiency with respect to direct PWM VSI connection to variable voltage battery supply. In this work, the modulation and control strategies are investigated, suitable for the best exploitation of the power system capabilities. Through a controlled coordination between H-bridge and VSI modulation patterns and control tasks, minimum PWM ripple contents and linear voltage transfer up to six-step operation are the targets. The resulting strategy, called cross-over voltage modulation, is reported for the first time together with the requested 3-Φ PWM enhancement called balanced envelopes modulation. CVM strategy is realized and experimental tests are reported showing very satisfactory results, achieving new automotive AC motor drive quality