Direct Single-Power-Conversion Bidirectional Grid-Connected Inverter Solving Commutation Problem

This article presents a novel direct single-power-conversion bidirectional grid-connected inverter for solving the commutation problem and a control strategy for it. The proposed inverter directly interfaces with a low-voltage battery and grid with only one power conversion stage and performs a bidirectional power conversion. The reliability of the proposed inverter is improved because the commutation capacitor eliminates the commutation problem by providing commutation paths in any switching case. The frequency compensation method converts the nonlinear power transfer characteristic into linear and makes grid current control easy. Furthermore, the interdependence of three control variables enables the control of the grid current using a simple equation. The proposed dual-mode control strategy increases the power capacity of the proposed inverter without increasing the turns ratio and decreasing the leakage inductance. The conduction losses can be reduced using this strategy. Additionally, the ZVS capability reduces the switching losses. These features of the proposed inverter and its control strategy enable the proposed inverter to achieve high efficiency and power quality with a simple structure. The theoretical concepts of the proposed inverter were experimentally verified using a 1-kW prototype.