Interlinking Converter to Improve Power Quality in Hybrid AC–DC Microgrids With Nonlinear Loads

To exploit the advancements of both ac and dc microgrids (MGs), hybrid ac-dc MGs (HMGs) have been considered. An interlinking converter (IC) is typically used to connect dc and ac MGs. In HMGs, the power quality is severely affected when nonlinear loads are connected to an ac bus. We developed an effective control scheme for the IC to maintain a sinusoidal point of common coupling (PCC) voltage under nonlinear load conditions in islanded HMGs. In the proposed control scheme, the IC controls the PCC voltage by providing harmonic currents caused by the nonlinear load as well as the active power sharing between dc distributed generation (DG) and ac DG. The system stability and controller design process were analyzed. Each power converter in the HMGs is controlled independently without a communication link, and the desired IC current is indirectly determined by considering the IC terminal voltage instead of the load current. Therefore, the control system can be implemented very easily with reduced cost. The performance of the proposed IC control scheme was verified by a simulation and experiment.