Modeling and Control of Hybrid Distribution Transformers for Simultaneous Grid Services

TL;DR

This paper develops a mathematical model and control strategy for hybrid distribution transformers that enable simultaneous grid services, improving power quality and renewable integration with simple control mechanisms.

Contribution

It introduces a comprehensive averaged model and a control scheme for HDTs with back-to-back converters, facilitating multiple grid services without added complexity.

Findings

Simulation confirms effective control of load voltage and reactive power.

HDTs can perform grid frequency regulation and load balancing.

Control approach is simple and easily implementable.

Abstract

Hybrid distribution transformers (HDTs) integrate conventional transformers with partially rated power electronic converters to improve power quality, enable advanced ancillary services and increase penetration of renewable energy sources in the national power grid. In this paper, we present an averaged mathematical model of a three-phase HDT equipped with two back-to-back voltage source converters connected in a series-shunt configuration. Cascaded PI controllers are designed in the synchronously rotating dq0 reference frame to regulate load voltage, compensate reactive power, achieve grid frequency regulation, and perform load phase balancing. Simulation results implemented in Python confirm that these simple yet effective control mechanisms allow HDTs to offer simultaneous grid services without introducing complexity. The complete model, control architecture, and implementation steps are detailed, enabling further validation and adoption.