Adaptive Fuzzy Tuning of Smart Transformer for Microgrid-Utility Power Interactions

Lack of effective control over the power flow is one of the main problems in the Point of Common Coupling (PCC) of the microgrid and the main utility. To tackle this issue, this paper is on developing a confident, simple, and low-cost way for smooth and bidirectional control of power transfer between the microgrid and the main utility. The proposed approach is based on smart transformer (ST) which is an isolated high-frequency power converter that consists high-frequency step-down tap-changer transformer and three-phase to single-phase matrix converters. These converters contribute to improve the microgrid power management during grid-connected mode. For the simultaneous control of voltage and frequency, the method of Dual Virtual Quadrature Source (DVQS) with sinusoidal duty cycle is proposed to effectively adjust the switching parameters during the fault between the microgrid and the main utility. Moreover, fuzzy logic contributes to a flexible control on active and reactive power flow management. To evaluate the performance of the proposed approach, simulation studies are established on a sample system and discussed in more depth.