Frequency Support of Micro Grid using Fleet of Electric Vehicles

Abstract

In the today s scenario, frequency deviation is a common issue in islanded microgrids (MG) due to the intermittent nature of renewable energy sources (RES). It generally occurs due to the mismatch between power generation and load demand of the MG. If the power generation by RES is more as compared to the load demand then frequency of the system increases on the contrary, if the load demand is more as compared to power generation then frequency of the system decreases. In order to overcome these deviations in frequency, it is very important to make the balance between load demand and power generation. This issue can be minimized by providing the inertia to the system. However, RES have low or no rotational mass and therefore, they are not able to provide the inertia to the system. On the other hand, it has been observed that virtual inertia to the system can be provided by using the energy storage system (ESS). Further, it has been found that electric vehicles (EVs) can behave as both storage and source of power for the MG. By considering these factors, concept of virtual synchronous generator (VSG) mechanism using a charging station (CS) is proposed to provide the inertia to the system where, a fleet of EVs parked in the CS acts as an ESS for MG. Case studies have been carried out to verify the frequency support of MG using VSG mechanism. In these case studies, irradiation level of the PV array and load of the MG system have been changed arbitrarily to induce the power mismatch in the system. Through simulation results, it has been verified that the frequency of the system can be supported by the bidirectional flow of power between the CS and MG using VSG control mechanism. Apart from this, sudden ingress and egress of EVs at the CS has been considered while providing the frequency support to the MG. However, the EVs which ingress and egress from the CS may have different battery voltage ratings with different charging needs.