Start-up circuit for an electric vehicle fast charger using SSICL technique and a slow estimator

With the increase in power rating of electric vehicle chargers, concerns regarding their integration to the grid have likewise grown. This paper investigates a novel technique for start-up of high-power fast electric vehicle (EV) charger using a solid-state inrush current limiter (SSICL). The circuit consists of three similar sets of bidirectional switch and limiting resistor that utilizes a control strategy based on a simple Kalman filter (KF) to suppress the converter start-up current and transient over-voltages. In fact, the built-up profile of the inrush current is dictated in accordance with the estimated current by the slow dynamic KF. Compared to alternatives, such as start-up resistors, the presented SSICL achieves faster start-up with comparable peak current, tends to provide lower distortion, and provides a good balance between speed and efficiency. Simulation and experimental results confirm that the proposed method can considerably suppress inrush currents, while improving the total harmonic distortion. Comparing the behaviour of the SSICL to other relevant techniques underlines the advantages of the proposed solution. Furthermore, although the focus of this paper is start-up of the fast EV chargers, the proposed circuit can act as an inrush-current limiter in most AC to DC converter structures.