Non-Linear Control of a DC Microgrid for Electric Vehicle Charging Stations

Abstract

Environmental concerns push governments to invest in renewable energy (RE). They are natural sources with a low carbon footprint and do not pollute locally. However, it is technically difficult to deploy high penetration of RE into the utility grid, due to the generation uncertainties and high installation costs, which are some of the most critical issues in RES use in this area. To address this issue, DC microgrids arise as a solution to integrate local distributed generation (DG) and storage, and to mitigate the issues related to AC/DC and DC/AC converters. Thanks to their main advantages for the power grid and energy consumers, microgrids have gained significant interest in recent years. By another side, the electric vehicles (EVs) market is expected to grow in the coming years, which represent a new load that must be properly managed to avoid grid issues. Thus, this paper discusses the operation of DC microgrid considering the introduction of EVs. A nonlinear control is presented, including the modeling of charging of EVs. The simulated DC microgrid includes solar PV, a battery, and a supercapacitor. Significant variations from PV generation were included to highlight the performance of the methodology. The results show that the voltage fluctuations are small, which provides the DC microgrid with the required voltage stability. Moreover, it has been demonstrated that DC microgrids can be integrated in isolated locations that are not connected to the main grid in view of the RESs and EVs.

Assessment of the Impact of Electric Vehicle Batteries in the Non-Linear Control of DC Microgrids

“…This work has assessed the impact of charging EVs in DC microgrids by using nonlinear control. The modeling of the batteries is more accurate than in [25], where a simplified model for batteries was considered. For both of the models, the non-linear control results in the adequate stability of the systems, with less than 1% of voltage deviations.…”

“…This part will focus on the battery model's connection (see Section 3.1) to the microgrid that was studied previously (see Section 2.1). Thus, the new model will be more realistic than the microgrid model created by [25]. The other interest is to observe the impact of a battery on the power grid of the MG-DC, so we will have results that are closer to reality.…”

“…The integration of the previously modelized battery on a microgrid is now explained. It is based on [25], where the authors developed a functional model of a microgrid in Simulink. They developed a "Non-linear DC microgrid" that remains as stable as possible (less than 5% variations), so that there is no disturbance during the charge of the EV.…”

“…In the model of [25], the output of V DC was created based on the previous equation, which depends on several parameters, including a current named I Load . Instead of having a fixed I Load , we will have a variable I Load .…”

“…Few works have proposed the operation of DC microgrids considering the introduction of EVs. In previous work, [25], the non-linear control of a DC microgrid considering EV charging was proposed. However, the presented model of the battery EV was simple.…”