At present,high voltage and high frequency have become the development trend of bidirectional power conversion systems(PCS).Therefore,the application of silicon carbide(SiC) devices in bidirectional energy storage converters is becoming more and more extensive.In order to achieve islanding protection in small and medium-power bidirectional PCS,and address the issue of increased grid connected hamonics caused by the frequency disturbance method during dectecting,a T-type three-level topology,a DSOGI phase-locked loop based on line voltage,and a grid connected current positive and negative sequence separation control strategy were adopted to design PCS.At the same time,an optimizied strategy for islanding detection was proposed,which can effectively reduce the harmonic content of grid connected current and can detect the islanding effects within the specified time for protection.Finally,a bidirectional PCS prototype was completed,which was verified that the optimal control strategy was correct and effective.
