Reduced Order AC Microgrid Model for Secondary Controller Design Using dq Reference Frame

Improving the design of primary and secondary level controllers of microgrids is of critical importance to microgrid deployment. Controller design and tuning rely heavily upon adequate, dynamic models of microgrids. In modeling of microgrids, there is always a compromise between accuracy and complexity as indicated by model order. Many of the currently available models found in the literature are reflective of system behavior but with high-order or less representative of system behavior with a low-order mathematical representation. In this paper, a reduced order, linear, inverter based, microgrid model based on the dq reference frame is developed. The order of the model is 2n (for n distributed generators (DG)) lower than the least of the orders of models suited for secondary controller design currently available. The system representation includes the commonly neglected cable impedance dynamics and the interconnection coupling between DG units. Static and dynamic model equations are utilized to capture strong correlations between the linear, reduced order (6n - 1 states for n DGs) model and non-linear system model in the transient (low frequency) and steady-state regions. The model developed is validated via a time domain simulation in the MATLAB/SIMULINK environment. The effect of the interconnection coupling between DGs on the eigenvalues is also presented.

Automated summary

Improving the design of primary and secondary level controllers of microgrids is crucial for microgrid deployment. This paper presents a reduced order, linear, inverter based, microgrid model and validates its effectiveness through simulation.