Stability Domain Analysis for Islanded Microgrid Considering N-1 Contingency

Abstract

The most popular approach used in controlling inverter-based microgrids is the droop control technique, characterized by its plug-and-play capability and independence from communication requirements. The control parameters, at the top of which the active and reactive droop gains, $m_{p}$ and $n_{q}$ , respectively, have been recently studied, evaluating their impact on stability. Furthermore, the stability domain chart is plotted in the $m_{p,max}{-n}_{q}$ plane identifying the stable range of the microgrid, enabling the microgrid operator to choose the desired stable operating point based on frequency, voltage, and power-sharing requirements. However, the microgrid is prone to abnormal conditions, such as network disconnection, distributed generator (DG) disconnection, and load disconnection, that also affect microgrid stability. Hence, this can have an impact on the stability domain and, consequently, the choice of droops for stable operation. Therefore, in this paper, several stability domain charts are proposed, considering all various contingencies. The proposed network disconnection, DG disconnection, and load disconnection domain charts have been combined to generate an overall stability domain chart considering $\boldsymbol {N} -1$ contingency. The proposed $\boldsymbol {N} -1$ contingency chart is of crucial importance in considering the microgrid stability for both normal and abnormal operations. $\boldsymbol {N} -1$ contingencies can be frequent in microgrid operation due to microgrid limited space and power nature. Hereby, the inclusion of their impact on microgrid stability provides better guidance for the tuning of the control parameters. Moreover, the proposed chart is tested and validated using time-domain simulations on MATLAB, considering different operating points. The simulation results highlight the significance of the stability domain chart for selecting the DG droop gains to maintain the microgrid stability considering $\boldsymbol {N} -1$ contingency. Further, real-time validation of the proposed domain of stability through OPAL-RT setup is analyzed to confirm the ability of practical controllers to respond to microgrid variations conditions in real-time operation.

Keywords

• Domain of stability
• N-1 contingency
• inverter-based micro-grid
• DG disconnection
• network disconnection