A novel distributed approach based reactive power support in microgrids

Microgrid is one of the suitable answers to handle the challenge of electricity demand and supply imbalance by integrating Renewable Energy Sources (RES) to the main grid without redesigning the distribution system. However, increased penetration of RES in the conventional power system has led to new challenges as well, such as loss of inertia, low short circuit ratio, difficulty in reactive power support, the problem of storage in islanded condition, which need to be handled properly. Among other challenges, the reactive power sharing is one of the major problems in a Microgrid that leads to the voltage limit violation and increase in losses. This paper proposes a new methodology to control the reactive power through the distributed approach by measuring locally the change in the Thevenin equivalent impedance across the terminals of Voltage Source Converter (VSC) due to the change in the load. A vector control in dq frame of reference by decoupling the active and reactive power is implemented by fixing the active power support from the VSC. The reactive power demand is computed based on the impedance seen by the controller at the Point of Common Coupling (PCC). This distributed approach has been implemented in a power system with Microgrid using PSIM simulation platform.