Dynamic Power Coupling Analysis of Droop Based Autonomous Microgrid Using Dynamic Relative Gain Array

The parallel operation of various voltage source inverter (VSIs) based distributed generation (DG) units in autonomous mode is ensured by sharing the load power in a decentralized manner using (P-f) and (Q-V) droop control framework. It is well established that as the X/R ratio of the feeder impedance interfacing DGs to the point of common coupling (PCC) decreases, there exist a Strong static coupling between active and reactive powers. However, when these DGs operate in droop control scheme there may exist a dynamic coupling between their active and reactive powers. In this work, dynamic relative gain array method is used to analyse the existence of dynamic coupling between the active and reactive powers of DGs in desired frequency range by formulating a reduced order multivariable transfer function model relating active power and reactive power of each DG with respect to their voltage angles and voltage magnitude.