Autonomous power balance in hybrid AC/DC microgrids

Abstract

A control paradigm is proposed in this paper for decentralized power balance in hybrid AC/DC Microgrids (MGs). In this technique, the AC and DC sub-grids can transact energy from or towards the other side based on their loading conditions. Hybrid MGs use an interlink converter (ILC) as a back-to-back bi-directional converter at the Point of Common Coupling (PCC) between the sub-grids. The main duty of the ILC unit is to maintain the loading balance between the sub-grids. For this purpose, a superimposed AC voltage on the network’s nominal DC voltage is utilized in the DC sub-grid. Also, the AC sub-grid is equipped with the conventional f/P droop control. The frequency of the superimposed AC voltage in the DC sub-grid and the AC network frequency in the AC sub-grid are used for estimating the loading percentage of each side. As a result, the ILC unit acts as a load for one side and concurrently as a source for the other side. The ILC controller adjusts the participation of this unit in a fully decentralized manner. Simulation studies via PLECS test the efficacy of the suggested control system.