Executive Summary :
|The transport sector is one of the major consumers of the conventional sources of power, so it is time to switch over to Electric Vehicles (EVs) as the general mode of transportation for reducing emissions. The proliferation of EVs in India is not up to the mark as compared to other developed nations. The major impediment lies with poor public charging infrastructures like fuel pumping stations and lack of Indian standards for EVs to suit our requirements. Given this recently, GoI has given a standard for AC and DC charging. Contemporary most of EV’s charging requirements are being fulfilled by the AC utility grid, which in turn is being powered through the burning of conventional fuels. So, the thought of reducing the emission, by just changing the culture of transportation medium not going to work. Moreover, the task is daunting due to poor/limited availability of utility power around various places in India. Due to such limitations, there is needed to explore solutions which may be easily integrated with the conventional utility to act as a supplementary source of power for EV infrastructure. In this proposal, a 20 kW modular power-dense EV charging infrastructure needs to be developed, powered through a hybrid PV and grid system for a sustainable solution for the EV charging infrastructure in India. The said system will house three converters, namely one unidirectional converter interface with PV, one isolated bidirectional converter interfaced with EV and other bidirectional converter interfaced with the grid. The system will not only reduce the dependency of charging infrastructure on the utility but also grid interface bidirectional converter may facilitate PV power transactions to the grid in case of excess generation. Moreover, the grid side converter rating will be fully utilized for solving power quality issues also. The proposed off-board DC-based fast charging systems through the design of a proper isolated dc-dc converter system will facilitate fast charging of multiple EV’s at a time at a rate above 2C. Fast charging requires high current through the converter and in case of sudden demand of high rate of charging current may cause a momentarily deep in the common DC bus voltage. To avoid such phenomena, the ultracapacitor (UC) is embedded on a common dc bus via an interleaved dc-dc converter. UC acts as a heavy power source to provide a gush of power in case of requirement through fast-acting semiconductor switches with minimal ripple and noise. The output voltage of EV side dc-dc converter is configurable as per the rating of the EV’s battery stack. The proposed system housing different converters need to be designed and fabricated in-house using modern coolMOS and optiMOS highly efficient semiconductor switches based on super junction technology. Further, a coordinated control methodology of different sources (PV, grid) via power electronics interface is needed to be embedded in the system for maximum utilization of the resources.
|Dr Avadh Pati, Assistant Professor, National Institute of Technology (NIT), Silchar, Dr Vishal Verma, Professor, Delhi Technological University (DTU), Delhi