Small Hydro Based Grid Forming Converter Having Power Sharing and Synchronization Capability With DFIG Based WECS

Abstract

In the presence of the utility grid, the inverter based resources such as wind, hydro and photovoltaic operate in the grid following mode, as the voltage and frequency are assigned by the utility grid. However, in remote areas, where the presence of grid is challenging, it is required to maintain stiff voltage and frequency at the point of common interconnection of loads in standalone mode. In this work, a unique configuration comprising doubly fed induction generator (DFIG) based wind energy conversion system (WECS), small hydro-solar photovoltaic (SH-PV) based hybrid microgrid is presented, where the local grid is formed by the SH-PV system combined with a battery energy storage (BES). Switching logics are developed for the small hydro based grid forming, machine side and load side converters in such a way that synchronization of the WECS with the SH-PV is smooth. Besides, active filter operation of the load side converter is also demonstrated. The proposed microgrid is tested under various transitional modes and gives an insight of interactions between these inverter based renewable energy sources. The hybrid microgrid presented depicts bidirectional flow of power. This way uninterrupted power is supplied to the local loads and also supports noncritical loads. The work concludes with a laboratory prototype to illustrate the operation of hybrid microgrid in numerous modes.