Modeling and Design of Proportional Integral Resonant Controller for Attenuation of Current Ripple in LLC Resonant Converter of Electric Vehicle Onboard Charger

The main objective of this paper is to apply a proportional integral resonant (PIR) controller to attenuate the second harmonic (100 Hz) current ripple in an electric vehicle onboard charger that originates from the rectified 50 Hz AC power grid mains. First, we obtain the small signal model of the LLC resonant converter by using a time domain simulation method. We then discuss the design process of a conventional proportional integral (PI) controller and the design process of a resonant (R) controller which is used in parallel with the PI controller to form the PIR controller. The (PI) controller is used to maintain the battery charging current constant while the (R) controller is used to attenuate the second harmonic current ripple by giving a sufficiently high gain specifically at 100 Hz during the constant current charging process. Simulation results are obtained for a 650 W LLC resonant converter of an electric vehicle onboard charger with 390 V DC-link voltage for a 48 V, 30 Ah lithium-ion (Li-ion) battery being charged in constant current mode. The results show significant attenuation for the second harmonic current ripple for the PIR controller when compared to using only the PI controller. By using the designed PIR controller, we can achieve higher power density, higher reliability, and lower cost for the designed onboard charger in addition to increasing the Li-ion battery lifespan when compared to conventional attenuation methods for low-frequency current ripple.