Efficient conditioning of energy in AFE-based Distributed Generation units

Distributed Generation (DG) systems are often fluctuating power sources and may cause a fluctuating voltage in the network common coupling point (PCC), causing the occurrence of flickers. To overcome such phenomenon, the voltage control on PCC is crucial. In the connection of the DG unit to the network, via an electric energy static conversion system with bidirectional power flow (AFE), the power quality (PQ) depends on the harmonic content of the current supplied to the PCC. The paper proposes a strategy, based on the control of both point PCC voltage and current in the network filter inductance, and point bus DC voltage, thus allowing to obtain a high quality for the AFE provided or absorbed power. A model-based approach is used, in order to design controllers with pre-fixed stability, performance and robustness characteristics. Specifically, a wind power plant is considered as an example of DG unit. Simulations performed in a Matlab/Simulink™ environment indicate that the proposed strategy achieves a high quality energy exchange.