Modulation Strategy and Control Scheme of AC-AC Boost Converter for Under Voltage Compensation

The under voltage is an essential issue for the distribution network, which troubles millions of users. Compared to the traditional load tap changer counterpart, to pursue flexible and deep voltage-dip compensation, the AC-AC boost converter with advanced modulation and control schemes is proposed in this paper. To avoid the short-circuit risk during commutation and dead-time sectors, the improved modulation strategy is proposed to ensure the bi-directional free-wheeling paths. Concerning the forward, reverse, commutation, and dead-time modes of the converter, the operation principles and current routines of the converter are comprehensively revealed. Besides, the output voltage feedback loop is comparatively studied to eliminate the circulating current and ensure the safe commutation. Meanwhile, considering the voltage distortion effect, the blind time of the commutation is also carefully designed. Finally, the 500 W AC-AC boost converter prototype is fabricated and tested. The experiments in steady-state and dynamics examine the validation of the proposed modulation and control. The findings prove the AC-AC boost converter is a preferred solution for the voltage-dip compensation of the distribution network in the future.