DESCRIPTION

In highly regulated energy industry, electricity Distribution System Operators (DSO) are obliged to compile with existing grid codes and have to maintain specific quality voltage standards for all customers, either they are located in urbanistic or rural areas. For this reason, Ignitis group DSO “Energijos Skirstymo Operatorius” (ESO) together with Ignitis Innovation Hub and “Baltijos Pažangių Technologijų Institutas” (BPTI) has launched a pilot project to test grid support battery systems in distant rural locations with weak low voltage grids.

SOLUTION

The aim of the project is to evaluate the technological feasibility of grid storage solution to delay costly and time-consuming grid reconstruction. Grid storage is seen as an opportunity to tackle voltage quality problems at the end of the long 2-4 km low voltage power lines. The 5kW unit with 10 kWh of storage in this particular case is used as flexible asset in peak-shaving mode.

Voltage fluctuations occur due to high resistance in long overhead lines – voltage starts to decrease rapidly after a certain consumption power threshold. The principle operational mode of the grid support system is to employ the storage solution in peak-shaving mode after certain power threshold is reached. In the peak-shaving mode, excess power consumption over certain threshold is covered automatically by storage system, thus limiting line voltage drop and improving power quality in whole line.

The scope of this project is bound with two pilot sites, where two different manufacturer’s equipment is deployed. From the first iteration of the project it is already seen as a positive solution, which allows to achieve voltage control without expanding or changing power lines. However, there are undoubtable challenges as well. The main issue with the hybrid grid support system is the compatibility and fluent communication between Battery Management System (BMS), Inverter and grid itself. This miscommunications or inconsistent reaction times are causing 50-150ms duration voltage ripples which affects the quality of electricity supply.

Topologically, these systems are located at the end of the power line, connected before the customer’s meter on the ESO’s side. A Lithium-Ion driven storage solution is placed inside thermally controlled isolated container, which is capable to ensure the right operational conditions, prolonging the life of the system.

Grid support battery system creates an opportunity to tackle grid quality issues in more flexible way without investing into the infrastructure, especially in rural areas and can be procured from the market as a flexibility service.

STATUS AND PROGRESS

Tested battery storage solutions can handle voltage issues in rural areas, although they have some reliability issues. Overall battery storage solutions are being evaluated in the context of flexibility services.