Auxiliary Commutated Resonant Pole-Based DC–AC Converter With Ultralow THD for Planar Actuation System With SiC Devices

Dc–ac converters with ultralow total harmonic distortion (THD) are key equipments for planar actuation system. Conventional interleaved half-bridge converters are challenged by zero-crossing distortion and dead-time effect. Diverse techniques have been developed to overcome these challenges, however, most of current methods are limited by hard switching or switching frequency variation. In this article, an ultralow THD auxiliary commutated resonant pole-based dc–ac converter is proposed to overcome these challenges. First, operation principle is analyzed, demonstrating its capability for constant switching frequency and full load range soft switching. Second, impacts of zero-crossing distortion and dead-time effect on both the interleaved half-bridge and the proposed converter are detailed. By considering dead-time (T_d), load, and switching frequency, the analysis indicates that the voltage error of the proposed converter is approximately 3% relative to that of the conventional scheme. Third, parameters design, which account for reactive power consumption and nonlinear output capacitance, guarantees 20 kHz large-signal bandwidth and 1.2 A soft switching threshold. Another important contribution is current self equilibrium, which benefits the safety operation. Finally, experimental results indicates that the converter achieves 10 A peak current, 20 kHz large-signal bandwidth, full load range soft switching, constant switching frequency, and minimum output current THD of 0.063%.