Coordinated control of Distributed Generation

This paper presents an approach to coordinate Distributed Generation (DG) such that quantities in an unbalanced distribution system are balanced and power factor corrected. Models for the DG and three-phase distribution network are combined to form a set of Differential Algebraic Equations (DAE) that represent the behavior of the distribution system. Two state-feedback controllers with reference inputs are presented for coordinated control of DG. Both are designed via linearization of the DAE model. The first uses an additional matrix selected so that the outputs match the reference values in steady-state while the second uses an internal model design with integral to drive the outputs to the reference values. The approach is demonstrated on models of 5-bus and 10-bus test systems with inverter-connected DG. The control objective for the 5-bus test system is to balance active line powers across the three phases as supplied from the transmission system. The control objective for the 10-bus system is to correct power factor on each phase as supplied from the transmission system. Robustness of the internal model controller is investigated for uncertainties (up to 25%) in line parameters and unknown step changes (up to 25%) in loads, and results show that control objectives are achieved in the presence of these uncertainties.