Bidirectional single-phase Solid-State Transformer using multi cell for volume reduction of high voltage capacitor

This paper proposes a simple circuit configuration and a control strategy of Solid-State Transformer (SST). In the proposed circuit, it is possible to reduce the volume of heat sinks and passive components by using low voltage switching device with low loss characteristic and high frequency operation. Moreover, the circuit employed with the proposed control strategy operates stably even when the ripple voltage is large. Besides, the bidirectional operation of the proposed circuit is also confirmed by simulation. From the simulation result, the capacitance in each cell of the primary side (high voltage side) can be minimized to only 3 μF for 10-kVA system. Moreover, a miniature model with three cells is tested to confirm the fundamental operation of the proposed circuit. As a results, the sinusoidal waveform of the input current is obtained without the large distortion. the total harmonic distortion (THD) of the input current is 2.55%. In addition, it is confirmed that the primary side capacitor voltage of each cell is kept constant without the balance control.