Research on the control of phase-shift controlled high-frequency link cycloconverter

High-frequency (HF) link circuit integrates with a cycloconverter-type dc/ac converter so as to realize a compact, light-weight and bidirectional power flow converter for electrical isolated conditions, such as UPS, new energy systems and special electrical motion systems. However, when the secondary side of HF transformer has no load, the stored magnetic energy in the leakage inductance lacks its pass to release itself and cause a voltage surge between the secondary terminals of HF transformer to threaten to the safety of power switches. A new method for both CVCF system and VVVF system is presented, it is composed of two parts, one is a full-bridge phase-shift controlled circuit in the primary side of HF transformer, which generates periodic and stable zero-voltage intervals, the other is a cycloconverter in the secondary side of HF transformer with a pulse-density-modulated (PDM) current regulator, which helps to realize zero-voltage switching(ZVS). Based on the analysis of circuit topologies and principles of operation, as for three-phase induction motor, experiments are carried out to verify the concept.