Adaptive Gain Tuning of Onboard Chargers to Mitigate Parameter Uncertainty in V2G Interfaces

A technical challenge of interfacing electric vehicles (EVs) to the grid is in the design of the LC or LCL filter. The filter must have the capability to meet both the EV automotive requirements and the distribution grid requirements such as current ripple and steady state error. Furthermore, the filter design must accommodate bidirectional energy flow and should be re-configurable for various grid types such as single-phase, three-phase, and three-phase four-wire grid systems. All these stringent requirements along with the fact that the input filter of the EV occupies 30% of the (onboard charger) OBC size, lead to a very difficult bottleneck to minimize the power density and cost. This paper proposes an adaptive gain tuning to allow using a powdered-core inductor that has a smaller size than its ferrite core counterpart. The main difference of the powdered core is that its inductance reduces linearly with the current passing through it, while ferrite cores inductance remains constant until it reaches the knee point where the inductance decreases sharply. The proposed adaptive gain tuning shows that the controller requirements can be met with the inductance value uncertainty and linearly changing core inductance.