Stabilization of Smart Transformer Based Islanded Meshed Hybrid Microgrid During Electric Vehicle Charging Transients

Smart transformer (ST)-based meshed hybrid microgrid is an attractive solution for interfacing various energy sources and loads, while achieving improved power management features. In the islanded operation of such ST-based meshed grid, battery energy storage system (BESS) maintains the low voltage (LV) dc link voltage and acts like a slack bus. During sudden changes in load like charging of electric vehicles (EVs), such a system can become unstable due to slower system response owing to right half plane zero, which is inherently present in BESS converters. This article proposes a method of stabilizing an ST-based islanded meshed hybrid microgrid during transients arising from EV charging. To maintain the system stability during such load transients, the meshed nature of the system is exploited by controlling the LVac voltage using ST LV converter operating in grid forming mode. This in turn enables a control of the total load in the LVac grid. The proposed scheme provides a simple yet effective method to stabilize meshed islanded system in spite of slower system dynamics. The design and stability analysis of the converters are presented to study the system performance with the proposed method. Simulation and experimental results verify the proposed control scheme.