Control of a three-phase active transformer integrating energy storage

Abstract

The high penetration of distributed energy sources is changing the paradigm of electrical networks control and management. Nowadays, power conversion systems associated to green energy plants are not only required to deliver power according to an MPPT algorithm, but should also participate in the regulation and operation of the power system, in the case of large scale systems, or provide advanced features to end users in the case of prosumers. This work proposes the use of an active transformer, incorporating series voltage regulation and current shunt regulation, through two converters in back-to-back configuration, which is able to provide all power quality services as well as resilience to end-users. This topology is advantageous in case of prosumers connected to weak and faulty grids. Moreover, the proposed active transformer also includes a battery so that island operation is offered as a service. Throughout the paper, the stability analyses and the implementation of an active transformer are presented, with special emphasis on the control of the series converter. The proposed topology is validated through real time simulations and an experimental prototype which includes a 300 kWh energy storage installation.