An optimal tracking power sharing controller for inverter-based generators in grid-connected mode

Abstract

In this work, an optimal power sharing controller for a three-phase Inverter-based Generator (IG) in a synchronous d-q reference frame is presented. The optimization of this controller is computed using a Linear-Quadratic (LQ) tracking index that measures the tracking error. This approach has many advantages regarding to stability and robustness over classical Proportional-Integral (PI) or Proportional-Resonant (PR) controllers that use droop functions for power sharing. In addition, a comprehensive model that represents a grid-connected IG sharing power to the main grid is developed using the superposition principle. This model integrates the Voltage-Current (V-I) and power sharing dynamics in a single state space expression. To the best of our knowledge, although there have been approaches in V-I and power sharing control that improve microgrid stability and transient response, there are no formal methods that integrate both controllers as a single entity. The results of this method were compared against a known Proportional-Resonant controller that use droop functions for power sharing. Results show that the optimal power sharing controller improves transient response, improves power decoupling, and also reduces the quadratic cost associated with microgrid states and inputs.