Unified Modeling, Control, and Stability for a Vehicle-to-Grid and Plug-In EV System

Abstract

Plug-in electric vehicle (PEV) is an emerging vehicle that can be directly charged from the power grid via properly designed vehicle-to-grid (V2G) interfaces that coordinate the energy flow between the grid and the connected PEV. The considered PEV structure involves an energy storage system (ESS) and a motor whereas suitable power electronic devices bridge the two subparts. In the proposed scheme, a hybrid ESS (HESS) is taken into account that achieves to overcome the related to the existing batteries limited capabilities, since it combines an energy dense battery and a power dense supercapacitor (SC). Bidirectional dc/dc converters are used as controlled power interfaces between the HESS part and the common dc-side connection point. The V2G interface includes an inverter that controls the power flow from/to the grid and a LCL filter applied to reduce the grid harmonics. The nonlinear mathematical description of the entire PEV-V2G system is developed, in a unified manner, while proper cascaded controllers based on the passivity property are proposed to operate the system in a reliable and desired way. The rigorous stability analysis obtained via advanced Lyapunov techniques ensures global asymptotic stability (GAS) of the entire system around its desired equilibrium by properly tuning the gains of the proposed controllers. The proposed scheme is verified by simulating the complete nonlinear plant and controller system while a further validation is conducted through a hardware in the loop (HIL) real time dSpace-based emulation.