Analysis and Design of a Novel Expandable AC-AC Boost Direct Converter

Aiming at the problems of high switching loss, limited voltage gain and complicated commutation control in the traditional alternating current-ac (AC-AC) converter, this paper further investigates a new scalable single-phase boost AC-AC converter based on intrinsic commutation and symmetric bipolar operation, further improves the circuit by optimizing the component parameters, and verifies it through simulation experiments. The topology combines the switched-capacitor (SC) technology with a high-frequency weekly waveform converter to achieve voltage stress equalization and gain scaling through input-series-output-parallel (ISOP) modular SC units, and utilizes the inductor current continuity characteristic and synchronous modulation strategy to accomplish zero-voltage switching (ZVS), which eliminates phase-commutation spikes and circulating current losses. The proposed structure innovatively integrates a polarity converter to realize step frequency conversion and inverting/non-inverting control of the output voltage through low-frequency switching pairs, while retaining the symmetric bipolar gain characteristics. Theoretical analysis shows that the converter can realize a wide range of boost voltage by adjusting the number of SC cell stages and duty cycle, and has continuous input current characteristics without additional filtering circuits. Simulation experiments verify the dynamic performance of the topology: the system exhibits optimal ripple (0.8 V) and efficiency (92%) at a critical damping (≈0.7), while the resonance frequency (87 kHz) effectively avoids switching disturbances. The results show that the proposed converter significantly outperforms the existing schemes in terms of efficiency (90%-95%), voltage stress suppression, and modular scalability, which makes it suitable for high power density scenarios such as new energy grid-connection and electric vehicle charging.