Operation Analysis for Seamless Charge and Discharge Control of High Efficiency Grid-Connected Bi-directional Power Conversion System for Storage Battery Systems with Bi-directional Switch Circuit Topology

Prototype Evaluation of Grid‐Connected Bidirectional Power Conversion System for Storage Battery Systems with Bidirectional Switch Circuit Topology

“…Figure 4 pertains to the switching sequence when the storage battery is discharged. As can be seen from comparison of the above discharging and charging sequences with switching sequences in literature [5], same switching sequences, irrespective of the polarity of ac output current i g , can be obtained by simply switching between the positive group S5 to S8 and the negative group S9 to S12. Switches performing phase-shift control in the bidirectional switch module operate according to the polarity of HF inverter's output voltage v t as well as ac output voltage v g and current i g .…”

“…For details of this compensation control, please refer to literature [5]. Now, phase-shift angle α in the secondary circuit is calculated through feedback control based on conventional control of grid-connected inverter combined with compensation for lagging current caused by leakage inductance of HF transformer.…”

“…The case of positive current i g is reported in literature [5] and is omitted here. Figures 4 and 5 illustrate sequences for one cycle of HF inverter in connected state when ac output current i g is negative.…”

“…As regards allocation of sequence numbers in this state flow, please refer to literature [5]. Therefore, we add mode change in step (i) to create a loop for reliable handling of current oscillation near zero cross even if power factor state has changed.…”

“…We previously reported that lagging-current compensation control can suppress the influence exerted on output current in the proposed system by leakage inductance of high-frequency transformer that occurs because of bidirectional power interchange in grid-connected operation and the use of bidirectional switches [4,5]. Verification was conducted by simulation and analysis so far, but in this paper, we report on experimental verification and discuss applicability of the proposed system to bidirectional power conversion for grid-connected storage battery systems.…”