Reduction of Switching Transients in Constant Current (CC)/Constant Voltage (CV) Mode of Electric Vehicles Battery Charging

Abstract

Optimum charging of electric vehicles is of great interest today. Researchers have worked upon different charge methodology for switching from constant current mode (CCM) to con- stant voltage mode (CVM). But, major problem occurs while transition are the switching tran- sients. Therefore, a suitable methodology for switching from CCM to CVM while charging the lithium-ion battery is to be implemented. Among the various methods used today, Schmitt trigger switching is the most reliable and efficient method for charging the lithium-ion battery. Therefore, this work adopts CCM/CVM mode of charging with Schmitt trigger switching. This helps in reducing switching losses and increasing the response time of the battery. For imple- menting the proposed scheme, a hardware for the boost converter is designed and the control- ling for the same is obtained using Opal-RT. PI controller for CCM and CVM is designed to regulate the output and generate the desired duty cycle. Tuning of the PI controller for CCM and CVM is obtained using loop shaping method. Switching between the two modes i.e. CCM and CVM is done using Schmitt trigger. The band limit of Schmitt trigger is set according to the capacitor ripple voltage. The controlling param- eter i.e. the duty cycle generated is applied to the IGBT switches using digital I/Os. The input parameters voltage and current are feedback using analog I/Os. Thus, the real-time results for battery charging i.e. voltage and current can be obtained accordingly.