Parameters Design of Stabilized Control Strategy for Smart Transformer-fed Grid

The interaction between the distributed energy resources (DERs) inverter and smart transformer (ST) could trigger harmonic oscillation problem of ST-fed Grid. To solve the problem, this paper proposes a second-order digital filter-based stabilized control strategy to enhance the stability of ST-fed grid. Then, analyzing from the perspective of zeros and poles of ST output impedance, a design criterion is proposed based on the relationship between the filter and the characteristic roots of the system. Finally, the effectiveness of the stabilized control strategy is verified by experiment.

I. Introduction

The smart transformer (ST) becomes a key equipment in power systems with high penetration of distributed energy resources (DERs) [1]. In contrast to traditional transformers, STs not only provide voltage transformation and electrical isolation but also enhance the grid's ability to accommodate DERs [2]. Additionally, STs offer auxiliary services such as reactive power compensation, impedance identification, and fault isolation, making them well-suited for improving system functionality and performance [3], [4].