A unified phase-shift modulation for optimized synchronization of parallel resonant inverters in high frequency power system

High frequency alternating current (HFAC) has already been applied in many power distribution systems due to outstanding merits. The circulation current control of the high frequency resonant inverter in parallel connection is more complicated than the low frequency counterpart. Methods from topology, modulation, and control perspectives have already been proposed; however, most of them are difficult to simultaneously accomplish the synchronization of magnitude and phase in high frequency circumstance. In this paper, a new modulation called as unified phase-shift modulation (PSM) is proposed to integrate the regulations of magnitude and phase. The unified PSM in steady state completely removes the modulation coupling between magnitude and phase so that the controllers of magnitude and phase can be independently accomplished without interactions. The operation scope of unified PSM is determined by zero voltage switching and total harmonic distortion of the resonant inverter. A prototype with two parallel inverters is established to verify the effectiveness with an operation frequency of 25 kHz and a full bridge output voltage of 40 V peak. The results of simulation and experiment prove that the unified PSM is superior over the existing PSM in HFAC circumstance. The controllers of magnitude and phase integrated by the proposed modulation can accomplish optimized output synchronization in the parallel single-stage resonant inverter.