Optimized Charge Scheduling of Electric Buses in a City Bus Network

Abstract

To promote environment-friendly commute within cities, governments across the world are increasing the footprint of electric vehicles in their public transport fleet. Despite electric buses being clean in terms of zero on-road emissions, their operation can have sudden impacts on the local distribution network and ultimately, on the power system load curve. With the introduction of a variety of electric vehicles by the next decade, this will not only impact the loading of distribution assets but also lead to burden on the system operator to manage the peaks and on the distribution utility to procure costlier peak power. Coordinated charge scheduling with the utility or through a charge point operator can help address this problem. By exploring the opportunity of charging at the electric bus depots during solar hours and periods of lean load, this paper proposes an approach to optimize the charge scheduling of the total electric bus fleet of a city with a goal to minimize the peak loading. A mathematical optimization framework has been created to optimize the charging schedule at individual bus depots considering operation of both CNG and E-buses for the city of Delhi, India. The results are encouraging and show improvement in the load factor and in improving the charging during solar hours. The results derived from the study suggest that a coordinated charge schedule can help in reducing the peak load of the utility thus helping to avoid costlier power purchase. The results from uncoordinated charging do not promote charging during solar hours since it adds to the evening peak and is concentrated at a few hours. The methodology presented in the paper can be useful for charge point operators and electric bus fleet owners to manage their operations in an optimal manner.