Patent ID: 8775835

Claim:
A method in a controller controlling a dynamic power compensator, the dynamic power compensator arranged to provide active and reactive power to an electric power system, the dynamic power compensator comprising a battery energy storage, the battery energy storage comprises two or more battery strings each battery strings comprising at least one battery unit, the method comprising the steps of: monitoring a state of charge of the battery energy storage, detecting a voltage level in the electric power system requiring increased delivery of the reactive power to the electric power system, and controlling the battery energy storage in dependence on the monitored state of charge and detected voltage level, wherein the step of controlling comprises sending open/close commands to breakers arranged within the battery energy storage for re-configuring the battery energy storage, wherein the two or more battery strings are re-configured by connecting one of the at least one battery units from a first battery string to another battery string, so that the battery unit of the first battery string is connected in series with the battery units of the other battery string, wherein the number of battery units in the other battery string is increased.