In the three-phase four-wire low-voltage micro grid, three-phase imbalance usually happens because of a large number of single-phase loads. In this situation, the traditional control method cannot effectively control the voltage and frequency stability when the low-voltage micro grid operates in the island mode. According to the characteristics of the three-phase four-wire low-voltage micro grid, this paper designs a single-phase independent control based on the droop control. This paper firstly uses the improved droop control considering that the impedance characteristic of the low voltage micro gird is mainly resistance, and also designs single-phase independent control to ensure the control system have the ability to run under the unbalanced loads. Then this paper designs a two-level control strategy to control the voltage and frequency in the micro grid during the island operation. Finally, a simulation analysis based on the proposed method is used to prove the effectiveness. A micro grid is set up on PSCAD, and verifies the effectiveness of the single-phase control strategy based on the improved droop control. The proposed method can also realize the requirement of the voltage and frequency stability during the island operation. At the same time, the control method proposed in this paper can achieve the control objective under the condition of unbalanced three-phase.
Research on frequency Control Strategy of micro grid including wind power and hybrid energy storage system
