Control of parallel-connected bidirectional AC-DC converters in stationary frame for microgrid application

With the penetration of renewable energy in modern power system, microgrid has become a popular application worldwide. In this paper, parallel-connected bidirectional converters for AC and DC hybrid microgrid application are proposed as an efficient interface. To reach the goal of bidirectional power conversion, both rectifier and inverter modes are analyzed. In order to achieve high performance operation, hierarchical control system is accomplished. The control system is designed in stationary frame, with harmonic compensation in parallel and no coupled terms between axes. In this control system, current/voltage controllers and droop controllers are reached in the first level. Controllers to restore the deviation caused by droop are achieved in the second level. To improve the performance in grid-connected operation, tertiary control can be involved. Theoretical analyses of main power circuit and control diagram are validated by simulation and experiment.