Nested control of plug-in electric vehicles for renewable power tracking

A robust strategy is proposed in this paper to simultaneously control the source and aggregate charging power of plug-in electric vehicles (PEVs). The charging flexibility of PEVs provides the power grid with control authority to cope with load fluctuations caused by the variation of grid-connected PEVs population and their instantaneous power demand. In this paper, a nested-loop control system consisting of an inner- and outer-loop is developed for aggregate charging power of PEVs. The inner-loop is used to control the charge rate of a fleet of grid-connected PEVs using sliding mode control theory. The outer-loop controller is then developed to adjust the renewable power source to avoid the inner-loop control saturation and the resulted drastic reference tracking error therein. The adjusted power is injected into a battery storage device and dispatched to the grid whenever the power demand is high. The closed-loop performance of the presented approach is demonstrated using real data from renewable sources.