A Practical Criteria for Unplanned Off-Grid Operation of Microgrid

A Practical Criteria for Unplanned Off-Grid Operation of Microgrid

연구 분야: Verification

학회: 2024 Boao New Power System International Forum - Power System and New Energy Technology Innovation Forum (NPSIF)

The development of Micro-Grid (MG) technology can significantly improve the smart level of power grid, and has become an important means to improve the reliability of power supply in weak power grids, such as mountain areas and islands. In the context of frequent extreme weather, weak power grids are highly vulnerable to electrical failures and natural disasters, and unplanned off-grid operation (UOGO) from grid-connection will become an important action scenario of smart MGs. It is a particularly key technique to enable MGs to automatically identify the triggering conditions of UOGO. A practical UOGO criterion is proposed here based on reactive power change rate of point of common coupling (PCC) in multi-port MG. Firstly, based on the electromagnetic principle of transformer, the characteristics of reactive power change of PCC (the low voltage side of main transformer) of MG are analyzed under the condition of main-grid drop-outs (i.e., power failure on the high voltage side of main transformer), and the practical criterion of UOGO based on the characteristics of reactive power change of PCC point is proposed. Taking a 10kV MG demonstration project in a southern county as an example, the time domain simulation model of the MG is then constructed, including hydropower unit and load model. Through the simulation, it is found that all the scenarios without off-grid operation requirement can be avoided by setting the criterion threshold reasonably, showing the feasibility and practicability of the proposed criterion.