One novel control strategy of the AC/DC bi-directional power converter in micro-grid

The bidirectional converter of AC/DC hybrid microgrid plays a crucial role in the stable operation and power allocation of power system. In order to improve the stability of microgrid, this paper proposes a novel AC/DC bidirectional converter control strategy to keep the power balance of AC/DC microgrid. The new control strategy of microgrid is different in grid-connected mode and islanding mode. In the dq coordinate system, the bidirectional converter is able to control the power flow of microgrid in grid-connected mode through the direct axis current value which is calculated by the outer loop control of DC voltage. When it operates in islanding mode, the bidirectional converter controls the power flow between AC and DC through the voltage difference between AC and DC buses. Unlike the traditional control strategy, the active power control loop is introduced in the new algorithm. Then the DC microgrid becomes a controllable unit to incorporate into the AC bus which can improve the stability and controllability of microgrid. After the analysis of the bidirectional converter, the control block diagram of the new control strategy is given. Comprehensive simulation results indicate that the system based on new control method is stable and effective.