Coordinated Control for Islanded DC Microgrid Based on Derivative of Bus Voltage

The unbalanced power generated by unintentional islanding is a tremendous challenge to the stable operation of the DC microgrid. When dealing with this challenge, the existing communication-free voltage-threshold-based coordinated control lags far behind the actual power variation, which exacerbates the risk of voltage violations in the microgrid. To address the drawback of the existing control, this paper proposes a new method based on the derivative of bus voltage. Firstly, based on the mathematical correlation between unbalanced power and the derivative of bus voltage, a coordination control strategy and its switching criterion before the battery energy storage system (BESS) exits operation is proposed. Meanwhile, we propose a communication-free approach to sense the operation state of the BESS based on the dynamic process of the derivative of bus voltage. Thus the information obtained under complicated circumstances could be further enriched. Subsequently, a new control strategy after BESS operates operation is established to coordinate different sources among the microgrid. Compared with the existing coordinated control methods, the proposed one can better utilize the information contained in the dynamic process of the bus voltage. Numerical results validate the effectiveness and advantages of the proposed method.