Grid impedance variation has the possibility of leading to voltage oscillation and control instability, which poses a serious problem to electric vehicle (EV) charger design. In response to this problem, this paper proposes a robust control approach that is capable of dealing with grid impedance variation and system uncertainties. The proposed dual-loop control strategy is composed of an outer-loop proportional–integral (PI) controller and an inner-loop robust state feedback controller with integral action. The benefits of control are maximized according to linear matrix inequality (LMI) techniques. This paper aims to address the effects of grid impedance variation by including the uncertainty model considering the potential varying parameters in the control design process. Additionally, the uncertainty model considers sixteen possible sets, which are described by variations in the four most important parameters: grid impedance, grid resistance, filter impedance, and filter resistance. The simulations suggest that the proposed controller maintains stable current regulation for uncertainty factors as high as γ = 3.3, where all closed-loop poles remain within the unit circle. For all the tested uncertainty levels, the grid-current tracks the reference of 10 A with a faster settling time at γ = 1.1 and no overshoot for higher uncertainty levels.

Single-stage single-phase onboard electric vehicle (EV) chargers are popular owing to their simple structure and high efficiency. However, their performance during grid connection is highly dependent on grid impedance characteristics. In a real-world scenario, it is hard to determine the exact value of grid impedance because it varies over time. This creates a challenge for a controller design that is based on a certain value of impedance. In this paper, a robust current controller is presented for a single-stage single-phase onboard EV charger, considering both L-filter and uncertain grid impedance characteristics. A state-space model of a single-stage single-phase onboard EV charger incorporating grid impedance uncertainty is developed. Based on the uncertain model, an LMI-based robust current controller is designed considering both filter and grid impedance uncertainties. The robust current controller is presented by considering an uncertain model represented by a polytopic model with sixteen vertex systems. An all-pass filter is used to generate an orthogonal signal for a dq-frame implementation. Simulation results are presented to prove the robust current controller’s performance and robustness during different grid impedance conditions.