Maximize integration of renewables and optimize technical losses by means of an improved control implemented on a smart transformer

The tests were carried out at the SYSLAB laboratory of the Technical University of Denmark within the research project ERIGrid, which provides access to the leading European laboratories. It was experimentally demonstrated that coordinated control of a smart transformer and distributed energy resources (DERs) such as photovoltaic (PV), wind, battery energy storage system (BESS), flexible loads and electric vehicles (EVs) is able to reduce technical losses caused by reverse power flow and improve grid stability and compliance with grid codes, when integrating high share of renewable generation.

transforma.smart   Smart Transformer, 20/0.4kV, 630kVA; 2 wind turbines of 10 and 11kW 3 PV arrays x 10kW; Diesel generation set, 24kW; B2B converter, 26kW; Vanadium battery, 12kW; Controllable load banks, 18kW; EV charging post and 3 electrical vehicles

Ormazabal challenge and solution:

To clearly assess the benefits of the control techniques, a set of representative key performance indicators were defined:

1. Maximize the amount of renewable generation in the grid (Hosting Capacity, kW-h)
2. Reduce technical power losses (financial incentive for distribution operator)
3. Improve grid stability by increasing the lifespan of power equipment

Rural (R) and urban (U) grid scenarios using three voltage control strategies: No Control (N), Tap control (T), Reactive power + Tap control (QT), based on real-time measurements from different nodes were considered. Afterwards, in order to test the viability of the control system in a close-to-real environment, a 24-hour flexible test configuration, including almost all the resources available in the laboratory, was performed.

Key benefits to client:

• Coordinated control of a smart transformer and DERs significantly enhances grid reliability, increases integration of renewable energy and improves lifespan of power system equipment.
• Only tap control of a smart transformer facilitates integration of renewable generation by 61.65% compared to the base case, when none control was used.
• Combined control of reactive power and tap control reduces technical losses by up to 9%.