The Study of Smart Distribution Transformer Based on a Bipolar Matrix Chopper

Dynamic states in the power grid - deep voltage sags and swells, voltage fluctuation - can cause faults and defects in sensitive loads and in consequence financial losses. This paper presents the concept of a smart distribution transformer, without DC energy storage, to mitigate up to 50% voltage sag/swell and voltage fluctuation and protect sensitive loads against voltage perturbation. The presented topology is based on a hybrid transformer (HT) with bipolar matrix chopper. The analyzed HT contains two main units: a conventional transformer realizing galvanic separation between source and load, and a bipolar matrix chopper for voltage control. The paper contains an operational description, theoretical analysis, simulation and experimental test results of 1 kVA rated power laboratory model, operating with open control loop. The main advantages of the proposed solution is a wide range of output voltage control (0 - 2U
_S
), galvanic separation (as in the case of a conventional transformer) and high reliability. One drawback is the special construction of the transformer with an additional secondary winding.