In this paper, a novel three-phase bidirectional interface is proposed by using only four active switches to simplify the hardware circuit and achieve unity power factor, sinusoidal input current, adjustable output voltage and bidirectional power flow capability. To ensure obtaining clean input current waveform, the current tracking mechanism is analyzed together with graphical aid and some critical design conditions are presented. Finally, a small-signal model is derived and, in addition to the feedback control, an instantaneous voltage detector is proposed for the added feedforward control to achieve almost zero output impedance and zero audio susceptibility. A prototype hardware circuit is constructed and some experimental results are presented for demonstration.
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